PHP set_error_handler() Function

The set_error_handler() function sets a user-defined error handler function.set_error_handler — Sets a user-defined error handler function

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.

Example -

<?php
// error handler function
function myErrorHandler($errno, $errstr, $errfile, $errline)
{
 if (!(error_reporting() & $errno)) {
 // This error code is not included in error_reporting, so let it fall
 // through to the standard PHP error handler
 return false;
 }

switch ($errno) {
 case E_USER_ERROR:
 echo "My ERROR [$errno] $errstr \n";
 echo " Fatal error on line $errline in file $errfile";
 echo ", PHP " . PHP_VERSION . " (" . PHP_OS . ") \n";
 echo "Aborting... \n";
 exit(1);
 break;

case E_USER_WARNING:
 echo "My WARNING [$errno] $errstr \n";
 break;

case E_USER_NOTICE:
 echo "My NOTICE [$errno] $errstr \n";
 break;

default:
 echo "Unknown error type: [$errno] $errstr \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:

Example -

Note:

The standard PHP error handler is completely bypassed if this function is used, and the user-defined error handler must terminate the script, die(), if necessary.

If errors occur before the script is executed the custom error handler cannot be used since it is not registered at that time.

Parameter	Description
errorhandler	Required. Specifies the name of the function to be run at errors
E_ALL\|E_STRICT	Optional. Specifies on which error report level the user-defined error will be shown. Default is "E_ALL"