What is the use of the symbol in PHP

Question

I have seen uses of   in front of certain functions  like the following    fileHandle    fopen  fileName   writeAttributes     What is the use of this symbol

User · Answer

Like already some answered before  The   operator suppresses all errors in PHP  including notices  warnings and even critical errors   BUT  Please  really do not use the   operator at all   Why   Well  because when you use the   operator for error supression  you have no clue at all where to start when an error occurs  I already had some  fun  with legacy code where some developers used the   operator quite often  Especially in cases like file operations  network calls  etc  Those are all cases where lots of developers recommend the usage of the   operator as this sometimes is out of scope when an error occurs here  for example a 3rdparty API could be unreachable  etc     But what s the point to still not use it  Let s have a look from two perspectives   As a developer  When   is used  I have absolutely no idea where to start  If there are hundreds or even thousands of function calls with   the error could be like everyhwere  No reasonable debugging possible in this case  And even if it is just a 3rdparty error - then it s just fine and you re done fast   -  Moreover  it s better to add enough details to the error log  so developers are able to decide easily if a log entry is something that must be checked further or if it s just a 3rdparty failure that is out of the developer s scope   As a user  Users don t care at all what the reason for an error is or not  Software is there for them to work  to finish a specific task  etc  They don t care if it s the developer s fault or a 3rdparty problem  Especially for the users  I strongly recommend to log all errors  even if they re out of scope  Maybe you ll notice that a specific API is offline frequently  What can you do  You can talk to your API partner and if they re not able to keep it stable  you should probably look for another partner   In short  You should know that there exists something like    knowledge is always good   but just do not use it  Many developers  especially those debugging code from others  will be very thankful

User · Answer

PHP supports one error control operator  the at sign      When prepended to an expression in PHP  any error messages that might be generated by that expression will be ignored   If you have set a custom error handler function with set error handler   then it will still get called  but this custom error handler can  and should  call error reporting   which will return 0 when the call that triggered the error was preceded by an      lt  php    Intentional file error     my file    file   non existent file   or     die   Failed opening file  error was   php errormsg         this works for any expression  not just functions   value     cache  key      will not issue a notice if the index  key doesn t exist     gt    Note -   1  The  -operator works only on expressions    2  A simple rule of thumb is  if you can take the value of something  you can prepend the   operator to it  For instance  you can prepend it to variables  function and include calls  constants  and so forth  You cannot prepend it to function or class definitions  or conditional structures such as if and foreach  and so forth   Warning -     Currently the     error-control operator prefix will even disable   error reporting for critical errors that will terminate script   execution  Among other things  this means that if you use     to   suppress errors from a certain function and either it isn t available   or has been mistyped  the script will die right there with no   indication as to why

User · Answer

It suppresses errors   See Error Control Operators in the manual      PHP supports one error control operator  the at sign      When prepended to an expression in PHP  any error messages that might be generated by that expression will be ignored       If you have set a custom error handler function with set error handler   then it will still get called  but this custom error handler can  and should  call error reporting   which will return 0 when the call that triggered the error was preceded by an

User · Answer

It might be worth adding here there are a few pointers when using the   you should be aware of  for a complete run down view this post  http   mstd eu index php 2016 06 30 php-rapid-fire-what-is-the-symbol-used-for-in-php    The error handler is still fired even with the   symbol prepended  it just means a error level of 0 is set  this will have to be handled appropriately in a custom error handler  Prepending a include with   will set all errors in the include file to an error level of 0

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Also note that despite errors being hidden  any custom error handler  set with set error handler  will still be executed

User · Answer

suppresses error messages   It is used in code snippets like    file get contents  http   www exaple com      If domain  http   www exaple com  is not accessible  an error will be shown  but with   nothing is not showed

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suppresses the error message thrown by the function  fopen throws an error when the file doesn t exit     symbol makes the execution to move to the next line even the file doesn t exists  My suggestion would be not using this in your local environment when you develop a PHP code

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If the open fails  an error of level E WARNING is generated  You may use   to suppress this warning

User · Answer

The   symbol is the error control operator  aka the  silence  or  shut-up  operator   It makes PHP suppress any error messages  notice  warning  fatal  etc  generated by the associated expression  It works just like a unary operator  for example  it has a precedence and associativity  Below are some examples    echo 1   0     generates  Parse error  syntax error  unexpected T ECHO  since     echo is not an expression  echo   1   0      suppressed  Warning  Division by zero     i   0     suppressed  Notice  Undefined variable  i     displayed  Warning  Division by zero      i   0      suppressed  Notice  Undefined variable  i     suppressed  Warning  Division by zero    c      POST  a        POST  b       suppressed  Notice  Undefined index  a     suppressed  Notice  Undefined index  b    c    foobar    echo  Script was not terminated      suppressed  Fatal error  Call to undefined function foobar       however  PHP did not  ignore  the error and terminated the    script because the error was  fatal    What exactly happens if you use a custom error handler instead of the standard PHP error handler      If you have set a custom error handler function with   set error handler   then it will still get called  but this custom   error handler can  and should  call error reporting   which will   return 0 when the call that triggered the error was preceded by an      This is illustrated in the following code example   function bad error handler  errno   errstr   errfile   errline   errcontext        echo   bad error handler    errstr       return true    set error handler  bad error handler    echo   1   0      prints   bad error handler   Division by zero    The error handler did not check if   symbol was in effect  The manual suggests the following   function better error handler  errno   errstr   errfile   errline   errcontext        if error reporting       0            echo   better error handler    errstr                take appropriate action     return true

User · Answer

Suppose we haven t used the     operator then our code would look like this    fileHandle   fopen  fileName   writeAttributes     And what if the file we are trying to open is not found  It will show an error message   To suppress the error message we are using the     operator like    fileHandle    fopen  fileName   writeAttributes

User · Answer

It suppresses error messages     see Error Control Operators in the PHP manual

[php] What is the use of the @ symbol in PHP?

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