Sets a user function (error_handler
) to handle errors in a script.
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()).
It is important to remember that the standard PHP error handler is completely bypassed for the error types specified by error_types
unless the callback function returns FALSE
. 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.
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 most of E_STRICT
raised in the file where set_error_handler() is called.
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.
A callback with the following signature. NULL
may be passed instead, to reset this handler to its default state. Instead of a function name, an array containing an object reference and a method name can also be supplied.
$errno
, string $errstr
[, string $errfile
[, int $errline
[, array $errcontext
]]] ) 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.
Returns a string containing the previously defined error handler (if any). If the built-in error handler is used NULL
is returned. NULL
is also returned in case of an error such as an invalid callback. If the previous error handler was a class method, this function will return an indexed array with the class and the method name.
error_handler
NULL
The error handler must return FALSE
to populate $php_errormsg.
The example below shows the handling of internal exceptions by triggering errors and handling them with a user defined function:
<?php // error handler function function myErrorHandler($errno, $errstr, $errfile, $errline) { if (!(error_reporting() & $errno)) { // This error code is not included in error_reporting return; } switch ($errno) { case E_USER_ERROR: echo "<b>My ERROR</b> [$errno] $errstr<br />\n"; echo " Fatal error on line $errline in file $errfile"; echo ", PHP " . PHP_VERSION . " (" . PHP_OS . ")<br />\n"; echo "Aborting...<br />\n"; exit(1); break; case E_USER_WARNING: echo "<b>My WARNING</b> [$errno] $errstr<br />\n"; break; case E_USER_NOTICE: echo "<b>My NOTICE</b> [$errno] $errstr<br />\n"; break; default: echo "Unknown error type: [$errno] $errstr<br />\n"; break; } /* Don't execute PHP internal error handler */ return true; } // function to test the error handling function scale_by_log($vect, $scale) { if (!is_numeric($scale) || $scale <= 0) { trigger_error("log(x) for x <= 0 is undefined, you used: scale = $scale", E_USER_ERROR); } if (!is_array($vect)) { trigger_error("Incorrect input vector, array of values expected", E_USER_WARNING); return null; } $temp = array(); foreach($vect as $pos => $value) { if (!is_numeric($value)) { trigger_error("Value at position $pos is not a number, using 0 (zero)", E_USER_NOTICE); $value = 0; } $temp[$pos] = log($scale) * $value; } 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 echo "----\nvector b - a notice (b = log(PI) * a)\n"; /* Value at position $pos is not a number, using 0 (zero) */ $b = scale_by_log($a, M_PI); print_r($b); // this is trouble, we pass a string instead of an array echo "----\nvector c - a warning\n"; /* Incorrect input vector, array of values expected */ $c = scale_by_log("not array", 2.3); var_dump($c); // NULL // this is a critical error, log of zero or negative number is undefined echo "----\nvector d - fatal error\n"; /* log(x) for x <= 0 is undefined, you used: scale = $scale" */ $d = scale_by_log($a, -2.5); var_dump($d); // Never reached ?>
The above example will output something similar to:
vector a Array ( [0] => 2 [1] => 3 [2] => foo [3] => 5.5 [4] => 43.3 [5] => 21.11 ) ---- vector b - a notice (b = log(PI) * a) <b>My NOTICE</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 - a warning <b>My WARNING</b> [512] Incorrect input vector, array of values expected<br /> NULL ---- vector d - fatal error <b>My ERROR</b> [256] log(x) for x <= 0 is undefined, you used: scale = -2.5<br /> Fatal error on line 35 in file trigger_error.php, PHP 5.2.1 (FreeBSD)<br /> Aborting...<br />
callback -
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