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set_error_handler --
Sets a user-defined error handler function
Description
mixed set_error_handler ( callback error_handler [, int error_types])
Sets a user function (error_handler) to handle
errors in a script. Returns a string containing the previously defined
error handler (if any), or FALSE on error. If the previous handler
was a class method, this function will return an indexed array with
the class and the method name.
This function can be used for defining your own way of handling errors
during runtime, for example in applications in which you need to do
cleanup of data/files when a critical error happens, or when you need
to trigger an error under certain conditions (using
trigger_error()).
The second parameter error_types was introduced in
PHP 5 and can be used to mask the triggering of the
error_handler function just like the error_reporting ini setting controls
which errors are shown. Without this mask set the
error_handler will be called for every error
regardless to the setting of the error_reporting setting.
The user function needs to accept two parameters: the error code, and a
string describing the error. From PHP 4.0.2, three optional
parameters are supplied: the filename in which the error occurred, the
line number in which the error occurred, and the context in which the
error occurred (an array that points to the active symbol table at the
point the error occurred). The function can be shown as:
handler ( int errno, string errstr [, string errfile [, int errline [, array errcontext]]])
errno
The first parameter, errno, contains the
level of the error raised, as an integer.
errstr
The second parameter, errstr, contains the
error message, as a string.
errfile
The third parameter is optional, errfile,
which contains the filename that the error was raised in, as a string.
errline
The fourth parameter is optional, errline,
which contains the line number the error was raised at, as an integer.
errcontext
The fifth parameter is optional, errcontext,
which is an array that points to the active symbol table at the point
the error occurred. In other words, errcontext
will contain an array of every variable that existed in the scope the
error was triggered in.
Note:
Instead of a function name, an array containing an object reference and
a method name can also be supplied. (Since PHP 4.3.0)
Note:
The following error types cannot be handled with a user defined
function: E_ERROR, E_PARSE,
E_CORE_ERROR, E_CORE_WARNING,
E_COMPILE_ERROR,
E_COMPILE_WARNING, and
E_STRICT.
The example below shows the handling of internal exceptions by
triggering errors and handling them with a user defined function:
Example 1.
Error handling with set_error_handler() and
trigger_error()
<?php
// redefine the user error constants - PHP 4 only define("FATAL", E_USER_ERROR); define("ERROR", E_USER_WARNING); define("WARNING", E_USER_NOTICE);
// set the error reporting level for this script error_reporting(FATAL | ERROR | WARNING);
// error handler function function myErrorHandler($errno, $errstr, $errfile, $errline) { switch ($errno) { case FATAL: echo "<b>FATAL</b> [$errno] $errstr<br />\n"; echo " Fatal error in line $errline of file $errfile"; echo ", PHP " . PHP_VERSION . " (" . PHP_OS . ")<br />\n"; echo "Aborting...<br />\n"; exit(1); break; case ERROR: echo "<b>ERROR</b> [$errno] $errstr<br />\n"; break; case WARNING: echo "<b>WARNING</b> [$errno] $errstr<br />\n"; break; default: echo "Unkown error type: [$errno] $errstr<br />\n"; break; } }
// function to test the error handling function scale_by_log($vect, $scale) { if (!is_numeric($scale) || $scale <= 0) { trigger_error("log(x) for x <= 0 is undefined, you used: scale = $scale", FATAL); }
if (!is_array($vect)) { trigger_error("Incorrect input vector, array of values expected", ERROR); return null; }
for ($i=0; $i<count($vect); $i++) { if (!is_numeric($vect[$i])) trigger_error("Value at position $i is not a number, using 0 (zero)", WARNING); $temp[$i] = log($scale) * $vect[$i]; } return $temp; }
// set to the user defined error handler $old_error_handler = set_error_handler("myErrorHandler");
// trigger some errors, first define a mixed array with a non-numeric item echo "vector a\n"; $a = array(2,3, "foo", 5.5, 43.3, 21.11); print_r($a);
// now generate second array, generating a warning echo "----\nvector b - a warning (b = log(PI) * a)\n"; $b = scale_by_log($a, M_PI); print_r($b);
// this is trouble, we pass a string instead of an array echo "----\nvector c - an error\n"; $c = scale_by_log("not array", 2.3); var_dump($c);
// this is a critical error, log of zero or negative number is undefined echo "----\nvector d - fatal error\n"; $d = scale_by_log($a, -2.5);
?>
And when you run this sample script, the output will be:
vector a
Array
(
[0] => 2
[1] => 3
[2] => foo
[3] => 5.5
[4] => 43.3
[5] => 21.11
)
----
vector b - a warning (b = log(PI) * a)
<b>WARNING</b> [1024] Value at position 2 is not a number, using 0 (zero)<br />
Array
(
[0] => 2.2894597716988
[1] => 3.4341896575482
[2] => 0
[3] => 6.2960143721717
[4] => 49.566804057279
[5] => 24.165247890281
)
----
vector c - an error
<b>ERROR</b> [512] Incorrect input vector, array of values expected<br />
NULL
----
vector d - fatal error
<b>FATAL</b> [256] log(x) for x <= 0 is undefined, you used: scale = -2.5<br />
Fatal error in line 36 of file trigger_error.php, PHP 4.0.2 (Linux)<br />
Aborting...<br />
It is important to remember that the standard PHP error handler is completely
bypassed. error_reporting() settings will have no effect
and your error handler will be called regardless - however you are still
able to read the current value of error_reporting and
act appropriately. Of particular note is that this value will be 0 if the
statement that caused the error was prepended by the
@ error-control
operator.
Also note that it is your responsibility to die() if
necessary. If the error-handler function returns, script execution
will continue with the next statement after the one that caused an error.
Note:
If errors occur before the script is executed (e.g. on file uploads) the custom
error handler cannot be called since it is not registered at that time.
Note:
The second parameter error_types was introduced
in PHP 5.
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