Why is die() used at the end of function that handles an Ajax request?

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What could go wrong if I am not using die(); after the function that handles an Ajax request?



I have noticed that almost all the WordPress Ajax-based code is using it.






ajax







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    up vote
    6
    down vote

    favorite
    2












    What could go wrong if I am not using die(); after the function that handles an Ajax request?



    I have noticed that almost all the WordPress Ajax-based code is using it.






    ajax







    share|improve this question

























      up vote
      6
      down vote

      favorite
      2









      up vote
      6
      down vote

      favorite
      2






      2





      What could go wrong if I am not using die(); after the function that handles an Ajax request?



      I have noticed that almost all the WordPress Ajax-based code is using it.






      ajax







      share|improve this question















      What could go wrong if I am not using die(); after the function that handles an Ajax request?



      I have noticed that almost all the WordPress Ajax-based code is using it.






      ajax




      ajax






      share|improve this question















      share|improve this question













      share|improve this question




      share|improve this question








      edited Sep 11 at 7:54









      Peter Mortensen

      1535




      1535










      asked Sep 10 at 7:59









      Latheesh V M Villa

      272114




      272114




















          2 Answers
          2






          active

          oldest

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          up vote
          12
          down vote



          accepted










          If you do not die, execution will continue and might generate extra output which might break whatever information you are trying to send from the server to the browser. Strictly speaking, you might not need to die, but there is very little point in taking the risk.



          In more general terms, WordPress Ajax shows its age and the lack of experience working with Ajax when it was designed. You should use the WordPress JSON routes instead, as they can have a better URL structure, and the programming structure is more logical and modular.






          share|improve this answer






















          • Thank you for answer. A little confused with extra output..if there is no data get from the request,how extra output get generated? Also will it add up the server resources?
            – Latheesh V M Villa
            Sep 10 at 8:07










          • because wordpress continues to run and will try to handle the url. If the execution will trigger plugins that do not properly check the context in which their code is being run you might get output (most likely some php error if they expect to be called only in other context)
            – Mark Kaplun
            Sep 10 at 8:10






          • 1




            admin-ajax.php always adds output if request is not stopped. So, unless the caller of the AJAX ignores the output, the die is basically required, even if the wrapper wp_die should be preferred because a function containing die is pretty-much impossible to test.
            – gmazzap♦
            Sep 10 at 18:19










          • tnx @gmazzap, been a long while since I looked at the details of that code
            – Mark Kaplun
            Sep 11 at 3:27










          • Worth noting that wp_die can also be hooked by other plugins (via wp_die_ajax_handler). Nobody wants to use die or exit, but if you're publishing a plugin there's a risk of conflict if you don't. I even handle my own output buffering due to themes and plugins that produce junk output mid-execution.
            – Tim
            Sep 11 at 11:07


















          up vote
          -1
          down vote













          WordPress should not require this and it suggests poor coding practices.



          When you make an Ajax request, the requested URL should generate a response with the data required (and also set the correct headers to say what type of data it is, e.g. JSON). Nothing else should be provided in the response except the required output.



          I work with PHP and JavaScript all the time - although not a WordPress developer - and was amused by the title of this question. If that's what WordPress does, that's awful. As indicated in the accepted answer, it's likely to be a way to stop any further output being included in the response. But of course that "further output" should never be part of the response to begin with.






          share|improve this answer


















          • 3




            Hi Andy, and welcome here! Regarding your answer, WP best-practice for AJAX is to use admin-ajax.php as the endpoind of the request, and that file literally always adds output if not stopped (see github.com/WordPress/WordPress/blob/master/wp-admin/…) So if you output some JSON from a callback, and don't call die (or wrapper wp_die) WP will add a "0" that will break the JSON, preventing correct parsing from caller (js probably). So, yes, I agree that in a well developed application one should not be required to die; in WordPress, on the other hand...
            – gmazzap♦
            Sep 10 at 18:17










          • @gmazzap yes when i was working with ajax i noticed "0" being added up if don't use wp_die
            – Latheesh V M Villa
            Sep 10 at 20:03










          • being "awful" is not a very useful description. there are many awful things in any code which had been around for more than a very trivial time. No code is ever perfect. If you are going to use only perfect code, you will have to write everything yourself starting with the CPU microcode
            – Mark Kaplun
            Sep 11 at 12:48










          • I'm trying to educate people by answering the question correctly. Using die() is not required, and never would be in a well-written PHP application. Analogies of CPU code are irrelevant and show a total lack of understanding. Maybe your definition of "awful" and mine are different. I don't use WP because it's littered with nonsense like this. I code (properly) in PHP all the time and am trying to help from a PHP perspective. You can either accept that WP has got this - and many other things - completely wrong. As this is a WP stack I guess the fans of it have a hard time with this.
            – Andy
            Sep 12 at 10:05











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          2 Answers
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          active

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          2 Answers
          2






          active

          oldest

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          active

          oldest

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          oldest

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          up vote
          12
          down vote



          accepted










          If you do not die, execution will continue and might generate extra output which might break whatever information you are trying to send from the server to the browser. Strictly speaking, you might not need to die, but there is very little point in taking the risk.



          In more general terms, WordPress Ajax shows its age and the lack of experience working with Ajax when it was designed. You should use the WordPress JSON routes instead, as they can have a better URL structure, and the programming structure is more logical and modular.






          share|improve this answer






















          • Thank you for answer. A little confused with extra output..if there is no data get from the request,how extra output get generated? Also will it add up the server resources?
            – Latheesh V M Villa
            Sep 10 at 8:07










          • because wordpress continues to run and will try to handle the url. If the execution will trigger plugins that do not properly check the context in which their code is being run you might get output (most likely some php error if they expect to be called only in other context)
            – Mark Kaplun
            Sep 10 at 8:10






          • 1




            admin-ajax.php always adds output if request is not stopped. So, unless the caller of the AJAX ignores the output, the die is basically required, even if the wrapper wp_die should be preferred because a function containing die is pretty-much impossible to test.
            – gmazzap♦
            Sep 10 at 18:19










          • tnx @gmazzap, been a long while since I looked at the details of that code
            – Mark Kaplun
            Sep 11 at 3:27










          • Worth noting that wp_die can also be hooked by other plugins (via wp_die_ajax_handler). Nobody wants to use die or exit, but if you're publishing a plugin there's a risk of conflict if you don't. I even handle my own output buffering due to themes and plugins that produce junk output mid-execution.
            – Tim
            Sep 11 at 11:07















          up vote
          12
          down vote



          accepted










          If you do not die, execution will continue and might generate extra output which might break whatever information you are trying to send from the server to the browser. Strictly speaking, you might not need to die, but there is very little point in taking the risk.



          In more general terms, WordPress Ajax shows its age and the lack of experience working with Ajax when it was designed. You should use the WordPress JSON routes instead, as they can have a better URL structure, and the programming structure is more logical and modular.






          share|improve this answer






















          • Thank you for answer. A little confused with extra output..if there is no data get from the request,how extra output get generated? Also will it add up the server resources?
            – Latheesh V M Villa
            Sep 10 at 8:07










          • because wordpress continues to run and will try to handle the url. If the execution will trigger plugins that do not properly check the context in which their code is being run you might get output (most likely some php error if they expect to be called only in other context)
            – Mark Kaplun
            Sep 10 at 8:10






          • 1




            admin-ajax.php always adds output if request is not stopped. So, unless the caller of the AJAX ignores the output, the die is basically required, even if the wrapper wp_die should be preferred because a function containing die is pretty-much impossible to test.
            – gmazzap♦
            Sep 10 at 18:19










          • tnx @gmazzap, been a long while since I looked at the details of that code
            – Mark Kaplun
            Sep 11 at 3:27










          • Worth noting that wp_die can also be hooked by other plugins (via wp_die_ajax_handler). Nobody wants to use die or exit, but if you're publishing a plugin there's a risk of conflict if you don't. I even handle my own output buffering due to themes and plugins that produce junk output mid-execution.
            – Tim
            Sep 11 at 11:07













          up vote
          12
          down vote



          accepted







          up vote
          12
          down vote



          accepted






          If you do not die, execution will continue and might generate extra output which might break whatever information you are trying to send from the server to the browser. Strictly speaking, you might not need to die, but there is very little point in taking the risk.



          In more general terms, WordPress Ajax shows its age and the lack of experience working with Ajax when it was designed. You should use the WordPress JSON routes instead, as they can have a better URL structure, and the programming structure is more logical and modular.






          share|improve this answer














          If you do not die, execution will continue and might generate extra output which might break whatever information you are trying to send from the server to the browser. Strictly speaking, you might not need to die, but there is very little point in taking the risk.



          In more general terms, WordPress Ajax shows its age and the lack of experience working with Ajax when it was designed. You should use the WordPress JSON routes instead, as they can have a better URL structure, and the programming structure is more logical and modular.







          share|improve this answer














          share|improve this answer



          share|improve this answer








          edited Sep 11 at 7:54









          Peter Mortensen

          1535




          1535










          answered Sep 10 at 8:02









          Mark Kaplun

          19.9k52654




          19.9k52654











          • Thank you for answer. A little confused with extra output..if there is no data get from the request,how extra output get generated? Also will it add up the server resources?
            – Latheesh V M Villa
            Sep 10 at 8:07










          • because wordpress continues to run and will try to handle the url. If the execution will trigger plugins that do not properly check the context in which their code is being run you might get output (most likely some php error if they expect to be called only in other context)
            – Mark Kaplun
            Sep 10 at 8:10






          • 1




            admin-ajax.php always adds output if request is not stopped. So, unless the caller of the AJAX ignores the output, the die is basically required, even if the wrapper wp_die should be preferred because a function containing die is pretty-much impossible to test.
            – gmazzap♦
            Sep 10 at 18:19










          • tnx @gmazzap, been a long while since I looked at the details of that code
            – Mark Kaplun
            Sep 11 at 3:27










          • Worth noting that wp_die can also be hooked by other plugins (via wp_die_ajax_handler). Nobody wants to use die or exit, but if you're publishing a plugin there's a risk of conflict if you don't. I even handle my own output buffering due to themes and plugins that produce junk output mid-execution.
            – Tim
            Sep 11 at 11:07

















          • Thank you for answer. A little confused with extra output..if there is no data get from the request,how extra output get generated? Also will it add up the server resources?
            – Latheesh V M Villa
            Sep 10 at 8:07










          • because wordpress continues to run and will try to handle the url. If the execution will trigger plugins that do not properly check the context in which their code is being run you might get output (most likely some php error if they expect to be called only in other context)
            – Mark Kaplun
            Sep 10 at 8:10






          • 1




            admin-ajax.php always adds output if request is not stopped. So, unless the caller of the AJAX ignores the output, the die is basically required, even if the wrapper wp_die should be preferred because a function containing die is pretty-much impossible to test.
            – gmazzap♦
            Sep 10 at 18:19










          • tnx @gmazzap, been a long while since I looked at the details of that code
            – Mark Kaplun
            Sep 11 at 3:27










          • Worth noting that wp_die can also be hooked by other plugins (via wp_die_ajax_handler). Nobody wants to use die or exit, but if you're publishing a plugin there's a risk of conflict if you don't. I even handle my own output buffering due to themes and plugins that produce junk output mid-execution.
            – Tim
            Sep 11 at 11:07
















          Thank you for answer. A little confused with extra output..if there is no data get from the request,how extra output get generated? Also will it add up the server resources?
          – Latheesh V M Villa
          Sep 10 at 8:07




          Thank you for answer. A little confused with extra output..if there is no data get from the request,how extra output get generated? Also will it add up the server resources?
          – Latheesh V M Villa
          Sep 10 at 8:07












          because wordpress continues to run and will try to handle the url. If the execution will trigger plugins that do not properly check the context in which their code is being run you might get output (most likely some php error if they expect to be called only in other context)
          – Mark Kaplun
          Sep 10 at 8:10




          because wordpress continues to run and will try to handle the url. If the execution will trigger plugins that do not properly check the context in which their code is being run you might get output (most likely some php error if they expect to be called only in other context)
          – Mark Kaplun
          Sep 10 at 8:10




          1




          1




          admin-ajax.php always adds output if request is not stopped. So, unless the caller of the AJAX ignores the output, the die is basically required, even if the wrapper wp_die should be preferred because a function containing die is pretty-much impossible to test.
          – gmazzap♦
          Sep 10 at 18:19




          admin-ajax.php always adds output if request is not stopped. So, unless the caller of the AJAX ignores the output, the die is basically required, even if the wrapper wp_die should be preferred because a function containing die is pretty-much impossible to test.
          – gmazzap♦
          Sep 10 at 18:19












          tnx @gmazzap, been a long while since I looked at the details of that code
          – Mark Kaplun
          Sep 11 at 3:27




          tnx @gmazzap, been a long while since I looked at the details of that code
          – Mark Kaplun
          Sep 11 at 3:27












          Worth noting that wp_die can also be hooked by other plugins (via wp_die_ajax_handler). Nobody wants to use die or exit, but if you're publishing a plugin there's a risk of conflict if you don't. I even handle my own output buffering due to themes and plugins that produce junk output mid-execution.
          – Tim
          Sep 11 at 11:07





          Worth noting that wp_die can also be hooked by other plugins (via wp_die_ajax_handler). Nobody wants to use die or exit, but if you're publishing a plugin there's a risk of conflict if you don't. I even handle my own output buffering due to themes and plugins that produce junk output mid-execution.
          – Tim
          Sep 11 at 11:07













          up vote
          -1
          down vote













          WordPress should not require this and it suggests poor coding practices.



          When you make an Ajax request, the requested URL should generate a response with the data required (and also set the correct headers to say what type of data it is, e.g. JSON). Nothing else should be provided in the response except the required output.



          I work with PHP and JavaScript all the time - although not a WordPress developer - and was amused by the title of this question. If that's what WordPress does, that's awful. As indicated in the accepted answer, it's likely to be a way to stop any further output being included in the response. But of course that "further output" should never be part of the response to begin with.






          share|improve this answer


















          • 3




            Hi Andy, and welcome here! Regarding your answer, WP best-practice for AJAX is to use admin-ajax.php as the endpoind of the request, and that file literally always adds output if not stopped (see github.com/WordPress/WordPress/blob/master/wp-admin/…) So if you output some JSON from a callback, and don't call die (or wrapper wp_die) WP will add a "0" that will break the JSON, preventing correct parsing from caller (js probably). So, yes, I agree that in a well developed application one should not be required to die; in WordPress, on the other hand...
            – gmazzap♦
            Sep 10 at 18:17










          • @gmazzap yes when i was working with ajax i noticed "0" being added up if don't use wp_die
            – Latheesh V M Villa
            Sep 10 at 20:03










          • being "awful" is not a very useful description. there are many awful things in any code which had been around for more than a very trivial time. No code is ever perfect. If you are going to use only perfect code, you will have to write everything yourself starting with the CPU microcode
            – Mark Kaplun
            Sep 11 at 12:48










          • I'm trying to educate people by answering the question correctly. Using die() is not required, and never would be in a well-written PHP application. Analogies of CPU code are irrelevant and show a total lack of understanding. Maybe your definition of "awful" and mine are different. I don't use WP because it's littered with nonsense like this. I code (properly) in PHP all the time and am trying to help from a PHP perspective. You can either accept that WP has got this - and many other things - completely wrong. As this is a WP stack I guess the fans of it have a hard time with this.
            – Andy
            Sep 12 at 10:05















          up vote
          -1
          down vote













          WordPress should not require this and it suggests poor coding practices.



          When you make an Ajax request, the requested URL should generate a response with the data required (and also set the correct headers to say what type of data it is, e.g. JSON). Nothing else should be provided in the response except the required output.



          I work with PHP and JavaScript all the time - although not a WordPress developer - and was amused by the title of this question. If that's what WordPress does, that's awful. As indicated in the accepted answer, it's likely to be a way to stop any further output being included in the response. But of course that "further output" should never be part of the response to begin with.






          share|improve this answer


















          • 3




            Hi Andy, and welcome here! Regarding your answer, WP best-practice for AJAX is to use admin-ajax.php as the endpoind of the request, and that file literally always adds output if not stopped (see github.com/WordPress/WordPress/blob/master/wp-admin/…) So if you output some JSON from a callback, and don't call die (or wrapper wp_die) WP will add a "0" that will break the JSON, preventing correct parsing from caller (js probably). So, yes, I agree that in a well developed application one should not be required to die; in WordPress, on the other hand...
            – gmazzap♦
            Sep 10 at 18:17










          • @gmazzap yes when i was working with ajax i noticed "0" being added up if don't use wp_die
            – Latheesh V M Villa
            Sep 10 at 20:03










          • being "awful" is not a very useful description. there are many awful things in any code which had been around for more than a very trivial time. No code is ever perfect. If you are going to use only perfect code, you will have to write everything yourself starting with the CPU microcode
            – Mark Kaplun
            Sep 11 at 12:48










          • I'm trying to educate people by answering the question correctly. Using die() is not required, and never would be in a well-written PHP application. Analogies of CPU code are irrelevant and show a total lack of understanding. Maybe your definition of "awful" and mine are different. I don't use WP because it's littered with nonsense like this. I code (properly) in PHP all the time and am trying to help from a PHP perspective. You can either accept that WP has got this - and many other things - completely wrong. As this is a WP stack I guess the fans of it have a hard time with this.
            – Andy
            Sep 12 at 10:05













          up vote
          -1
          down vote










          up vote
          -1
          down vote









          WordPress should not require this and it suggests poor coding practices.



          When you make an Ajax request, the requested URL should generate a response with the data required (and also set the correct headers to say what type of data it is, e.g. JSON). Nothing else should be provided in the response except the required output.



          I work with PHP and JavaScript all the time - although not a WordPress developer - and was amused by the title of this question. If that's what WordPress does, that's awful. As indicated in the accepted answer, it's likely to be a way to stop any further output being included in the response. But of course that "further output" should never be part of the response to begin with.






          share|improve this answer














          WordPress should not require this and it suggests poor coding practices.



          When you make an Ajax request, the requested URL should generate a response with the data required (and also set the correct headers to say what type of data it is, e.g. JSON). Nothing else should be provided in the response except the required output.



          I work with PHP and JavaScript all the time - although not a WordPress developer - and was amused by the title of this question. If that's what WordPress does, that's awful. As indicated in the accepted answer, it's likely to be a way to stop any further output being included in the response. But of course that "further output" should never be part of the response to begin with.







          share|improve this answer














          share|improve this answer



          share|improve this answer








          edited Sep 11 at 7:54









          Peter Mortensen

          1535




          1535










          answered Sep 10 at 14:40









          Andy

          1153




          1153







          • 3




            Hi Andy, and welcome here! Regarding your answer, WP best-practice for AJAX is to use admin-ajax.php as the endpoind of the request, and that file literally always adds output if not stopped (see github.com/WordPress/WordPress/blob/master/wp-admin/…) So if you output some JSON from a callback, and don't call die (or wrapper wp_die) WP will add a "0" that will break the JSON, preventing correct parsing from caller (js probably). So, yes, I agree that in a well developed application one should not be required to die; in WordPress, on the other hand...
            – gmazzap♦
            Sep 10 at 18:17










          • @gmazzap yes when i was working with ajax i noticed "0" being added up if don't use wp_die
            – Latheesh V M Villa
            Sep 10 at 20:03










          • being "awful" is not a very useful description. there are many awful things in any code which had been around for more than a very trivial time. No code is ever perfect. If you are going to use only perfect code, you will have to write everything yourself starting with the CPU microcode
            – Mark Kaplun
            Sep 11 at 12:48










          • I'm trying to educate people by answering the question correctly. Using die() is not required, and never would be in a well-written PHP application. Analogies of CPU code are irrelevant and show a total lack of understanding. Maybe your definition of "awful" and mine are different. I don't use WP because it's littered with nonsense like this. I code (properly) in PHP all the time and am trying to help from a PHP perspective. You can either accept that WP has got this - and many other things - completely wrong. As this is a WP stack I guess the fans of it have a hard time with this.
            – Andy
            Sep 12 at 10:05













          • 3




            Hi Andy, and welcome here! Regarding your answer, WP best-practice for AJAX is to use admin-ajax.php as the endpoind of the request, and that file literally always adds output if not stopped (see github.com/WordPress/WordPress/blob/master/wp-admin/…) So if you output some JSON from a callback, and don't call die (or wrapper wp_die) WP will add a "0" that will break the JSON, preventing correct parsing from caller (js probably). So, yes, I agree that in a well developed application one should not be required to die; in WordPress, on the other hand...
            – gmazzap♦
            Sep 10 at 18:17










          • @gmazzap yes when i was working with ajax i noticed "0" being added up if don't use wp_die
            – Latheesh V M Villa
            Sep 10 at 20:03










          • being "awful" is not a very useful description. there are many awful things in any code which had been around for more than a very trivial time. No code is ever perfect. If you are going to use only perfect code, you will have to write everything yourself starting with the CPU microcode
            – Mark Kaplun
            Sep 11 at 12:48










          • I'm trying to educate people by answering the question correctly. Using die() is not required, and never would be in a well-written PHP application. Analogies of CPU code are irrelevant and show a total lack of understanding. Maybe your definition of "awful" and mine are different. I don't use WP because it's littered with nonsense like this. I code (properly) in PHP all the time and am trying to help from a PHP perspective. You can either accept that WP has got this - and many other things - completely wrong. As this is a WP stack I guess the fans of it have a hard time with this.
            – Andy
            Sep 12 at 10:05








          3




          3




          Hi Andy, and welcome here! Regarding your answer, WP best-practice for AJAX is to use admin-ajax.php as the endpoind of the request, and that file literally always adds output if not stopped (see github.com/WordPress/WordPress/blob/master/wp-admin/…) So if you output some JSON from a callback, and don't call die (or wrapper wp_die) WP will add a "0" that will break the JSON, preventing correct parsing from caller (js probably). So, yes, I agree that in a well developed application one should not be required to die; in WordPress, on the other hand...
          – gmazzap♦
          Sep 10 at 18:17




          Hi Andy, and welcome here! Regarding your answer, WP best-practice for AJAX is to use admin-ajax.php as the endpoind of the request, and that file literally always adds output if not stopped (see github.com/WordPress/WordPress/blob/master/wp-admin/…) So if you output some JSON from a callback, and don't call die (or wrapper wp_die) WP will add a "0" that will break the JSON, preventing correct parsing from caller (js probably). So, yes, I agree that in a well developed application one should not be required to die; in WordPress, on the other hand...
          – gmazzap♦
          Sep 10 at 18:17












          @gmazzap yes when i was working with ajax i noticed "0" being added up if don't use wp_die
          – Latheesh V M Villa
          Sep 10 at 20:03




          @gmazzap yes when i was working with ajax i noticed "0" being added up if don't use wp_die
          – Latheesh V M Villa
          Sep 10 at 20:03












          being "awful" is not a very useful description. there are many awful things in any code which had been around for more than a very trivial time. No code is ever perfect. If you are going to use only perfect code, you will have to write everything yourself starting with the CPU microcode
          – Mark Kaplun
          Sep 11 at 12:48




          being "awful" is not a very useful description. there are many awful things in any code which had been around for more than a very trivial time. No code is ever perfect. If you are going to use only perfect code, you will have to write everything yourself starting with the CPU microcode
          – Mark Kaplun
          Sep 11 at 12:48












          I'm trying to educate people by answering the question correctly. Using die() is not required, and never would be in a well-written PHP application. Analogies of CPU code are irrelevant and show a total lack of understanding. Maybe your definition of "awful" and mine are different. I don't use WP because it's littered with nonsense like this. I code (properly) in PHP all the time and am trying to help from a PHP perspective. You can either accept that WP has got this - and many other things - completely wrong. As this is a WP stack I guess the fans of it have a hard time with this.
          – Andy
          Sep 12 at 10:05





          I'm trying to educate people by answering the question correctly. Using die() is not required, and never would be in a well-written PHP application. Analogies of CPU code are irrelevant and show a total lack of understanding. Maybe your definition of "awful" and mine are different. I don't use WP because it's littered with nonsense like this. I code (properly) in PHP all the time and am trying to help from a PHP perspective. You can either accept that WP has got this - and many other things - completely wrong. As this is a WP stack I guess the fans of it have a hard time with this.
          – Andy
          Sep 12 at 10:05


















           

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