errorcontrol.xml

<?xml version="1.0" encoding="utf-8"?>
<sect1 xml:id="language.operators.errorcontrol">
 <title>Error Control Operators</title>
 <titleabbrev>Error Control</titleabbrev>
 <simpara>
  PHP supports one error control operator: the at sign (<literal>@</literal>).
  When prepended to an expression in PHP, any diagnostic error that might
  be generated by that expression will be suppressed.
 </simpara>
 <para>
  If a custom error handler function is set with
  <function>set_error_handler</function>, it will still be called even though
  the diagnostic has been suppressed.
 </para>

 <warning>
  <para>
   Prior to PHP 8.0.0, the <function>error_reporting</function> called inside the custom error handler
   always returned <literal>0</literal> if the error was suppressed by the <literal>@</literal> operator.
   As of PHP 8.0.0, it returns the value of this (bitwise) expression:
   <literal>E_ERROR | E_CORE_ERROR | E_COMPILE_ERROR | E_USER_ERROR | E_RECOVERABLE_ERROR | E_PARSE</literal>.
  </para>
 </warning>

 <simpara>
  Any error message generated by the expression is available in the <literal>"message"</literal>
  element of the array returned by <function>error_get_last</function>.
  The result of that function will change on each error, so it needs to be checked early.
 </simpara>
 <para>
  <example>
   <title>Intentional file error</title>
   <programlisting role="php">
<![CDATA[
<?php
$my_file = @file ('non_existent_file') or
    die ("Failed opening file: error was '" . error_get_last()['message'] . "'");
?>
]]>
   </programlisting>
  </example>
 </para>
 <para>
  <example>
   <title>Suppressing Expressions</title>
   <programlisting role="php">
<![CDATA[
<?php
// this works for any expression, not just functions:
$value = @$cache[$key];
// will not issue a notice if the index $key doesn't exist.
?>
]]>
   </programlisting>
  </example>
 </para>
 <note>
  <simpara>
   The <literal>@</literal>-operator works only on
   <link linkend="language.expressions">expressions</link>.
   A simple rule of thumb is: if one can take the value of something,
   then one can prepend the <literal>@</literal> operator to it.
   For instance, it can be prepended to variables, functions calls,
   certain language construct calls (e.g. <function>include</function>),
   and so forth.
   It cannot be prepended to function or class definitions,
   or conditional structures such as <literal>if</literal> and
   &foreach;, and so forth.
  </simpara>
 </note>
 <warning>
  <para>
   Prior to PHP 8.0.0, it was possible for the <literal>@</literal> operator
   to disable critical errors that will terminate script execution.
   For example, prepending <literal>@</literal> to a call of a function
   which did not exist, by being unavailable or mistyped, would cause
   the script to terminate with no indication as to why.
  </para>
 </warning>

 <sect2 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>error_reporting</function></member>
    <member><link linkend="ref.errorfunc">Error Handling and Logging functions</link></member>
   </simplelist>
  </para>
 </sect2>
</sect1>