How do you debug PHP scripts

Question

How do you debug PHP scripts   I am aware of basic debugging such as using the Error Reporting  The breakpoint debugging in PHPEclipse is also quite useful   What is the best  in terms of fast and easy  way to debug in phpStorm or any other IDE

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Nusphere is also a good debugger for php nusphere

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I often use CakePHP when Rails isn t possible  To debug errors I usually find the error log in the tmp folder and tail it in the terminal with the command     tail -f app tmp logs error log   It give s you running dialog from cake of what is going on  which is pretty handy  if you want to output something to it mid code you can use    this- gt log  xxxx      This can usually give you a good idea of what is going on wrong

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1 for print r    Use it to dump out the contents of an object or variable  To make it more readable  do it with a pre tag so you don t need to view source    echo   lt pre gt    print r  arrayOrObject     Also var dump  thing  - this is very useful to see the type of subthings

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Depending on the issue I like a combination of error reporting E ALL  mixed with echo tests  to find the offending line file the error happened in initally  you KNOW it s not always the line file php tells you right    IDE brace matching  to resolve  Parse error  syntax error  unexpected  end  issues   and print r    exit  dumps  real programmers view the source  p     You also can t beat phpdebug  check sourceforge  with  memory get usage     and  memory get peak usage     to find the problem areas

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i use zend studio for eclipse with the built in debugger  Its still slow compared to debugging with eclipse pdt with xdebug  Hopefully they will fix those issues  the speed has improved over the recent releases but still stepping over things takes 2-3 seconds  The zend firefox toolbar really makes things easy  debug next page  current page  etc   Also it provides a profiler that will benchmark your code and provide pie-charts  execution time  etc

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Output buffering is very useful if you don t want to mess up your output  I do this in a one-liner which I can comment uncomment at will    ob start   var dump    user error ob get contents     ob get clean

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There are many PHP debugging techniques that can save you countless hours when coding  An effective but basic debugging technique is to simply turn on error reporting  Another slightly more advanced technique involves using print statements  which can help pinpoint more elusive bugs by displaying what is actually going onto the screen  PHPeclipse is an Eclipse plug-in that can highlight common syntax errors and can be used in conjunction with a debugger to set breakpoints   display errors   Off error reporting   E ALL  display errors   On   and also used  error log    console log

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XDebug is essential for development  I install it before any other extension  It gives you stack traces on any error and you can enable profiling easily   For a quick look at a data structure use var dump    Don t use print r   because you ll have to surround it with  lt pre gt  and it only prints one var at a time    lt  php var dump   FILE      LINE      REQUEST     gt    For a real debugging environment the best I ve found is Komodo IDE but it costs

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Manual debugging is generally quicker for me - var dump   and debug print backtrace   are all the tools you need to arm your logic with

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Xdebug  by Derick Rethans  is very good  I used it some time ago and found it was not so easy to install  Once you re done  you won t understand how you managed without it  -   There is a good article on Zend Developer Zone  installing on Linux doesn t seem any easier  and even a Firefox plugin  which I never used

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Xdebug and the DBGp plugin for Notepad   for heavy duty bug hunting  FirePHP for lightweight stuff  Quick and dirty  Nothing beats dBug

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The most of bugs can be found easily by simply var dumping some of key variables  but it obviously depends on what kind of application you develop   For a more complex algorithms the step breakpoint watch functions are very helpful  if not necessary

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PhpEdit has a built in debugger  but I usually end up using echo    and print r    the old fashioned way

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I ve used the Zend Studio  5 5   together with Zend Platform  That gives proper debugging  breakpoints stepping over the code etc   although at a price

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PHP DBG  The Interactive Stepthrough PHP Debugger implemented as a SAPI module which can give give you complete control over the environment without impacting the functionality or performance of your code  It aims to be a lightweight  powerful  easy to use debugging platform for PHP 5 4  and it s shipped out-of-box with PHP 5 6   Features includes    Stepthrough Debugging Flexible Breakpoints  Class Method  Function  File Line  Address  Opcode  Easy Access to PHP with built-in eval   Easy Access to Currently Executing Code Userland API SAPI Agnostic - Easily Integrated PHP Configuration File Support JIT Super Globals - Set Your Own   Optional readline Support - Comfortable Terminal Operation Remote Debugging Support - Bundled Java GUI Easy Operation   See the screenshots       Home page  http   phpdbg com   PHP Error - Better error reporting for PHP  This is very easy to use library  actually a file  to debug your PHP scripts   The only thing that you need to do is to include one file as below  at the beginning on your code    require  php error php     php error reportErrors      Then all errors will give you info such as backtrace  code context  function arguments  server variables  etc  For example       Features include    trivial to use  it s just one file errors displayed in the browser for normal and ajaxy requests AJAX requests are paused  allowing you to automatically re-run them makes errors as strict as possible  encourages code quality  and tends to improve performance  code snippets across the whole stack trace provides more information  such as full function signatures  fixes some error messages which are just plain wrong syntax highlighting looks pretty  customization manually turn it on and off run specific sections without error reporting ignore files allowing you to avoid highlighting code in your stack trace application files  these are prioritized when an error strikes    Home page  http   phperror net   GitHub  https   github com JosephLenton PHP-Error  My fork  with extra fixes   https   github com kenorb-contrib PHP-Error  DTrace  If your system supports DTrace dynamic tracing  installed by default on OS X  and your PHP is compiled with the DTrace probes enabled  --enable-dtrace  which should be by default  this command can help you to debug PHP script with no time   sudo dtrace -qn  php    function-entry   printf   Y  PHP function-entry  t s s s   in  s  d n   walltimestamp  copyinstr arg3   copyinstr arg4   copyinstr arg0   basename copyinstr arg1     int arg2        So given the following alias has been added into your rc files  e g     bashrc     bash aliases    alias trace-php  sudo dtrace -qn  php    function-entry   printf    Y  PHP function-entry  t s s s   in  s  d n    walltimestamp  copyinstr arg3   copyinstr arg4   copyinstr arg0   basename copyinstr arg1     int arg2         you may trace your script with easy to remember alias  trace-php   Here is more advanced dtrace script  just save it into dtruss-php d  make it executable  chmod  x dtruss-php d  and run      usr sbin dtrace -Zs   See  https   github com kenorb dtruss-lamp blob master dtruss-php d   pragma D option quiet  php    compile-file-entry       printf   Y  PHP compile-file-entry  t s   s  n   walltimestamp  basename copyinstr arg0    copyinstr arg1       php    compile-file-return       printf   Y  PHP compile-file-return  t s   s  n   walltimestamp  basename copyinstr arg0    basename copyinstr arg1        php    error       printf   Y  PHP error message  t s in  s  d n   walltimestamp  copyinstr arg0   basename copyinstr arg1     int arg2      php    exception-caught       printf   Y  PHP exception-caught  t s n   walltimestamp  copyinstr arg0       php    exception-thrown       printf   Y  PHP exception-thrown  t s n   walltimestamp  copyinstr arg0       php    execute-entry       printf   Y  PHP execute-entry  t s  d n   walltimestamp  basename copyinstr arg0     int arg1      php    execute-return       printf   Y  PHP execute-return  t s  d n   walltimestamp  basename copyinstr arg0     int arg1      php    function-entry       printf   Y  PHP function-entry  t s s s   in  s  d n   walltimestamp  copyinstr arg3   copyinstr arg4   copyinstr arg0   basename copyinstr arg1     int arg2      php    function-return       printf   Y  PHP function-return  t s s s   in  s  d n   walltimestamp  copyinstr arg3   copyinstr arg4   copyinstr arg0   basename copyinstr arg1     int arg2      php    request-shutdown       printf   Y  PHP request-shutdown  t s at  s via  s n   walltimestamp  basename copyinstr arg0    copyinstr arg1   copyinstr arg2       php    request-startup       printf   Y  PHP request-startup  t s at  s via  s n   walltimestamp  basename copyinstr arg0    copyinstr arg1   copyinstr arg2        Home page  dtruss-lamp at GitHub  Here is simple usage    Run  sudo dtruss-php d  On another terminal run  php -r  phpinfo        To test that  you can go to any docroot with index php and run PHP builtin server by   php -S localhost 8080   After that you can access the site at http   localhost 8080   or choose whatever port is convenient for you   From there access some pages to see the trace output   Note  Dtrace is available on OS X by default  on Linux you probably need dtrace4linux or check for some other alternatives   See  Using PHP and DTrace at php net    SystemTap  Alternatively check for SystemTap tracing by installing SystemTap SDT development package  e g  yum install systemtap-sdt-devel    Here is example script  all probes stp  for tracing all core PHP static probe points throughout the duration of a running PHP script with SystemTap   probe process  sapi cli php   provider  php   mark  compile  file  entry         printf  Probe compile  file  entry n        printf    compile file  s n   user string  arg1        printf    compile file translated  s n   user string  arg2      probe process  sapi cli php   provider  php   mark  compile  file  return         printf  Probe compile  file  return n        printf    compile file  s n   user string  arg1        printf    compile file translated  s n   user string  arg2      probe process  sapi cli php   provider  php   mark  error         printf  Probe error n        printf    errormsg  s n   user string  arg1        printf    request file  s n   user string  arg2        printf    lineno  d n    arg3     probe process  sapi cli php   provider  php   mark  exception  caught         printf  Probe exception  caught n        printf    classname  s n   user string  arg1      probe process  sapi cli php   provider  php   mark  exception  thrown         printf  Probe exception  thrown n        printf    classname  s n   user string  arg1      probe process  sapi cli php   provider  php   mark  execute  entry         printf  Probe execute  entry n        printf    request file  s n   user string  arg1        printf    lineno  d n    arg2     probe process  sapi cli php   provider  php   mark  execute  return         printf  Probe execute  return n        printf    request file  s n   user string  arg1        printf    lineno  d n    arg2     probe process  sapi cli php   provider  php   mark  function  entry         printf  Probe function  entry n        printf    function name  s n   user string  arg1        printf    request file  s n   user string  arg2        printf    lineno  d n    arg3       printf    classname  s n   user string  arg4        printf    scope  s n   user string  arg5      probe process  sapi cli php   provider  php   mark  function  return         printf  Probe function  return   s n   user string  arg1        printf   function name  s n   user string  arg1        printf    request file  s n   user string  arg2        printf    lineno  d n    arg3       printf    classname  s n   user string  arg4        printf    scope  s n   user string  arg5      probe process  sapi cli php   provider  php   mark  request  shutdown         printf  Probe request  shutdown n        printf    file  s n   user string  arg1        printf    request uri  s n   user string  arg2        printf    request method  s n   user string  arg3      probe process  sapi cli php   provider  php   mark  request  startup         printf  Probe request  startup n        printf    file  s n   user string  arg1        printf    request uri  s n   user string  arg2        printf    request method  s n   user string  arg3        Usage   stap -c  sapi cli php test php  all probes stp   See  Using SystemTap with PHP DTrace Static Probes at php net

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Usually I find create a custom log function able to save on file  store debug info  and eventually re-print on a common footer   You can also override common Exception class  so that this type of debugging is semi-automated

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1  I use print r    In TextMate  I have a snippet for  pre  which expands to this   echo   lt pre gt    print r    echo   lt  pre gt      2  I use Xdebug  but haven t been able to get the GUI to work right on my Mac  It at least prints out a readable version of the stack trace

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In a production environment  I log relevant data to the server s error log with error log

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Try Eclipse PDT to setup an Eclipse environment that has debugging features like you mentioned  The ability to step into the code is a much better way to debug then the old method of var dump and print at various points to see where your flow goes wrong  When all else fails though and all I have is SSH and vim I still var dump   die   to find where the code goes south

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I use Netbeans with XDebug   Check it out at its website for docs on how to configure it  http   php netbeans org

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In all honesty  a combination of print and print r   to print out the variables  I know that many prefer to use other more advanced methods but I find this the easiest to use   I will say that I didn t fully appreciate this until I did some Microprocessor programming at Uni and was not able to use even this

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I use Netbeans with XDebug and the Easy XDebug FireFox Add-on   The add-on is essential when you debug MVC projects  because the normal way XDebug runs in Netbeans is to register the dbug session via the url  With the add-on installed in FireFox  you would set your Netbeans project properties -  Run Configuratuion -  Advanced and select  Do Not Open Web Browser  You can now set your break points and start the debugging session with Ctrl-F5 as usual  Open FireFox and right-click the Add-on icon in the right bottom corner to start monitoring for breakpoints  When the code reaches the breakpoint it will stop and you can inspect your variable states and call-stack

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This is my little debug environment   error reporting -1   assert options ASSERT ACTIVE  1   assert options ASSERT WARNING  0   assert options ASSERT BAIL  0   assert options ASSERT QUIET EVAL  0   assert options ASSERT CALLBACK   assert callcack    set error handler  error handler    set exception handler  exception handler    register shutdown function  shutdown handler     function assert callcack  file   line   message        throw new Customizable Exception  message  null   file   line      function error handler  errno   error   file   line   vars        if   errno     0      errno  amp  error reporting        0            return             throw new Customizable Exception  error   errno   file   line      function exception handler Exception  e           Do what ever      echo   lt pre gt    print r  e  true     lt  pre gt        exit     function shutdown handler         try           if  null      error   error get last                  throw new Customizable Exception  error  message     error  type     error  file     error  line                     catch  Exception  e            exception handler  e            class Customizable Exception extends Exception       public function   construct  message   null   code   null   file   null   line   null            if   code     null                parent    construct  message             else               parent    construct  message   code                     if   file     null                 this- gt file    file                    if   line     null                 this- gt line    line

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The integrated debuggers where you can watch the values of variable change as you step through code are really cool  They do  however  require software setup on the server and a certain amount of configuration on the client  Both of which require periodic maintenance to keep in good working order   A print r is easy to write and is guaranteed to work in any setup

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For the really gritty problems that would be too time consuming to use print r echo to figure out I use my IDE s  PhpEd  debugging feature   Unlike other IDEs I ve used  PhpEd requires pretty much no setup   the only reason I don t use it for any problems I encounter is that it s painfully slow   I m not sure that slowness is specific to PhpEd or any php debugger   PhpEd is not free but I believe it uses one of the open-source debuggers  like XDebug previously mentioned  anyway   The benefit with PhpEd  again  is that it requires no setup which I have found really pretty tedious in the past

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You can use Firephp an add-on to firebug to debug php in the same environment as javascript   I also use Xdebug mentioned earlier for profiling php

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PhpEd is really good  You can step into over out of functions  You can run ad-hoc code  inspect variables  change variables  It is amazing

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Komodo IDE works well with xdebug  even for the remore debugging  It needs minimum amount of configuration  All you need is a version of php that Komodo can use locally to step through the code on a breakpoint  If you have the script imported into komodo project  then you can set breakpoints with a mouse-click just how you would set it inside eclipse for debugging a java program  Remote debugging is obviously more tricky to get it to work correctly   you might have to map the remote url with a php script in your workspace   than a local debugging setup which is pretty easy to configure if you are on a MAC or a linux desktop

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Well  to some degree it depends on where things are going south  That s the first thing I try to isolate  and then I ll use echo print r   as necessary   NB  You guys know that you can pass true as a second argument to print r   and it ll return the output instead of printing it  E g    echo   lt pre gt   print r  var  true    lt  pre gt

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print r  debug backtrace       or something like that  -

[php] How do you debug PHP scripts?

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