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set_error_handler
Sets a user-defined error handler function
Description
callablenull set_error_handler(callablenull $callback , int $error_levels = E_ALL )
This function can be used to define custom error handlers during runtime,
for example in applications which need to do file/data cleanup when a critical
error happens, or when triggering an error in response to 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_levels
unless the callback function returns false .
error_reporting settings will have no effect and the
error handler will be called regardless - however, it's still possible to
read the current value of
error_reporting and act
appropriately.
Also note that it is the handler's responsibility to stop the
script's execution if necessary by calling exit. 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 independent of where they were raised, 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.
Parameters
-
callback
-
If null is passed, the handler is reset to its default state.
Otherwise, the handler is a callback with the following signature:
bool handler( int $errno , string $errstr , string $errfile = ?, int $errline = ?, array $errcontext = ? )
-
errno
-
The first parameter,
errno , will be passed the
level of the error raised, as an integer.
-
errstr
-
The second parameter,
errstr , will be passed the
error message, as a string.
-
errfile
-
If the callback accepts a third parameter,
errfile ,
it will be passed the filename that the error was raised in, as a string.
-
errline
-
If the callback accepts a fourth parameter,
errline ,
it will be passed the line number where the error was raised, as an integer.
-
errcontext
-
If the callback accepts a fifth parameter,
errcontext ,
it will be passed an array that points to the active symbol table at the
point the error occurred. In other words, errcontext
will contain an array of every variable that existed in the scope the
error was triggered in.
User error handlers must not modify the error context.
Warning
This parameter has been DEPRECATED as of PHP 7.2.0,
and REMOVED as of PHP 8.0.0. If the function defines
this parameter without a default, an error of "too few arguments" will be
raised when it is called.
If the function returns false then the normal error handler continues.
-
error_levels
-
Can be used to mask the triggering of the
callback function just like the error_reporting ini setting
controls which errors are shown. Without this mask set the
callback will be called for every error
regardless to the setting of the error_reporting setting.
Return Values
Returns the previously defined error handler (if any). If
the built-in error handler is used null is returned.
If the previous error handler
was a class method, this function will return an indexed array with the class
and the method name.
Examples
Example #1 Error handling with set_error_handler and trigger_error
The example below shows the handling of internal exceptions by
triggering errors and handling them with a user defined function:
<?php
// error handler function
function myErrorHandler($errno, $errstr, $errfile, $errline)
{
if (!(error_reporting() & $errno)) {
// This error code is not included in error_reporting, so let it fall
// through to the standard PHP error handler
return false;
}
// $errstr may need to be escaped:
$errstr = htmlspecialchars($errstr);
switch ($errno) {
case E_USER_ERROR:
echo "<b>My ERROR</b> [$errno] $errstr<br />\n";
echo " Fatal error on line $errline in file $errfile";
echo ", PHP " . PHP_VERSION . " (" . PHP_OS . ")<br />\n";
echo "Aborting...<br />\n";
exit(1);
case E_USER_WARNING:
echo "<b>My WARNING</b> [$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 />
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