Can I try catch a warning

Question

I need to catch some warnings being thrown from some php native functions and then handle them   Specifically   array dns get record    string  hostname     int  type  DNS ANY     array  amp  authns     array  amp  addtl          It throws a warning when the DNS query fails   try catch doesn t work because a warning is not an exception   I now have 2 options    set error handler seems like overkill because I have to use it to filter every warning in the page  is this true    Adjust error reporting display so these warnings don t get echoed to screen  then check the return value  if it s false  no records is found for hostname    What s the best practice here

User · Answer

The solution that really works turned out to be setting simple error handler with E WARNING parameter  like so   set error handler  warning handler   E WARNING   dns get record      restore error handler     function warning handler  errno   errstr        do something

User · Answer

Normaly you should never use   unless this is the only solution  In that specific case the function dns check record should be use first to know if the record exists

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FolderStructure   index php   Script File logs   Folder for log Every warning and Errors CustomException php   Custom exception File   CustomException php        Custom error handler    function handleError  code   description   file   null   line   null   context   null         displayErrors   ini get  display errors          displayErrors   strtolower  displayErrors       if  error reporting       0     displayErrors      on             return false            list  error   log    mapErrorCode  code        data   array           timestamp    gt  date  Y-m-d H i s u   time              level    gt   log           code    gt   code           type    gt   error           description    gt   description           file    gt   file           line    gt   line           context    gt   context           path    gt   file           message    gt   error           code            description     in       file      line      line                   data   array map  htmlentities   data       return fileLog json encode  data             This method is used to write data in file    param mixed  logData    param string  fileName    return boolean    function fileLog  logData   fileName   ERROR LOG FILE         fh   fopen  fileName   a         if  is array  logData              logData   print r  logData  1              status   fwrite  fh   logData     n        fclose  fh          file   file get contents  filename          content          file             file put contents  content        return   status    true   false           Map an error code into an Error word  and log location       param int  code Error code to map    return array Array of error word  and log location     function mapErrorCode  code         error    log   null      switch   code            case E PARSE          case E ERROR          case E CORE ERROR          case E COMPILE ERROR          case E USER ERROR               error    Fatal Error                log   LOG ERR              break          case E WARNING          case E USER WARNING          case E COMPILE WARNING          case E RECOVERABLE ERROR               error    Warning                log   LOG WARNING              break          case E NOTICE          case E USER NOTICE               error    Notice                log   LOG NOTICE              break          case E STRICT               error    Strict                log   LOG NOTICE              break          case E DEPRECATED          case E USER DEPRECATED               error    Deprecated                log   LOG NOTICE              break          default               break            return array  error   log       calling custom error handler set error handler  handleError      just include above file into your script file like this  index php  error reporting E ALL   ini set  display errors    off    define  ERROR LOG FILE    logs app errors log     include once  CustomException php   echo  a     here undefined variable warning will be logged into logs app errors log

User · Answer

You should probably try to get rid of the warning completely  but if that s not possible  you can prepend the call with    i e   dns get record       and then use any information you can get to figure out if the warning happened or not

User · Answer

Be careful with the   operator - while it suppresses warnings it also suppresses fatal errors  I spent a lot of time debugging a problem in a system where someone had written  mysql query          and the problem was that mysql support was not loaded into PHP and it threw a silent fatal error  It will be safe for those things that are part of the PHP core but please use it with care   bob mypc    php -a Interactive shell  php  gt  echo  something       this will just silently die      No further output - good luck debugging this   bob mypc    php -a Interactive shell  php  gt  echo something       lets try it again but don t suppress the error PHP Fatal error   Call to undefined function something   in php shell code on line 1 PHP Stack trace  PHP   1   main    php shell code 0 bob mypc       This time we can see why it failed

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I would only recommend using   to suppress warnings when it s a straight forward operation  e g   prop      high   width -  depth    to skip division by zero warnings   However in most cases it s better to handle

User · Answer

If dns get record   fails  it should return FALSE  so you can suppress the warning with   and then check the return value

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try checking whether it returns some boolean value then you can simply put it as a condition  I encountered this with the oci execute      which was returning some violation with my unique keys   ex  oci parse  res    oracle pl sql     if oci execute      do something

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I wanted to try catch a warning  but at the same time keep the usual warning error logging  e g  in  var log apache2 error log   for which the handler has to return false  However  since the  throw new     statement basically interrupts the execution  one then has to do the  wrap in function  trick  also discussed in    Is there a static way to throw exception in php  Or  in brief     function throwErrorException  errstr   null  code   null   errno   null   errfile   null   errline   null        throw new ErrorException  errstr  0   errno   errfile   errline         function warning handler  errno   errstr   errfile   errline  array  errcontext        return false  amp  amp  throwErrorException  errstr  0   errno   errfile   errline         error log  AAA      will never run after throw        Do execute PHP internal error handler          return false    will never run after throw             set error handler  warning handler   E WARNING           try       mkdir  path  0777  true       catch  Exception  e        echo  e- gt getMessage                       EDIT  after closer inspection  it turns out it doesn t work  the  return false  amp  amp  throwErrorException      will  basically  not throw the exception  and just log in the error log  removing the  false  amp  amp   part  as in  return throwErrorException       will make the exception throwing work  but will then not log in the error log    I d still keep this posted  though  as I haven t seen this behavior documented elsewhere

User · Answer

Set and restore error handler One possibility is to set your own error handler before the call and restore the previous error handler later with restore error handler    set error handler function        ignore errors        dns get record    restore error handler     You could build on this idea and write a re-usable error handler that logs the errors for you  set error handler   logger   onSilencedError     dns get record    restore error handler     Turning errors into exceptions You can use set error handler   and the ErrorException class to turn all php errors into exceptions  set error handler function  errno   errstr   errfile   errline           error was suppressed with the  -operator     if  0     error reporting              return false                 throw new ErrorException  errstr  0   errno   errfile   errline        try       dns get record      catch  ErrorException  e                  The important thing to note when using your own error handler is that it will bypass the error reporting setting and pass all errors  notices  warnings  etc   to your error handler  You can set a second argument on set error handler   to define which error types you want to receive  or access the current setting using       error reporting   inside the error handler  Suppressing the warning Another possibility is to suppress the call with the   operator and check the return value of dns get record   afterwards  But I d advise against this as errors warnings are triggered to be handled  not to be suppressed

User · Answer

Combining these lines of code around a file get contents   call to an external url helped me handle warnings like  failed to open stream  Connection timed out  much better   set error handler function   err severity   err msg   err file   err line  array  err context        throw new ErrorException   err msg  0   err severity   err file   err line       E WARNING   try        iResult   file get contents  sUrl     catch  Exception  e         this- gt sErrorMsg    e- gt getMessage      restore error handler      This solution works within object context  too  You could use it in a function   public function myContentGetter  sUrl          code above       return  iResult

[php] Can I try/catch a warning?

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