set_error_handler
(PHP 4 >= 4.0.1, PHP 5) set_error_handler — Sets a user-defined error handler function
Description
mixed set_error_handler
( callback $error_handler
[, int $error_types
] )
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. 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.
Parameters
-
error_handler
-
The user function needs to accept two parameters: the error code, and a
string describing the error. Then there are three optional parameters
that may be 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 $errcontext
]]] )
-
errno
-
The first parameter, errno
, contains the
level of the error raised, as an integer.
-
errstr
-
The second parameter, errstr
, contains the
error message, as a string.
-
errfile
-
The third parameter is optional, errfile
,
which contains the filename that the error was raised in, as a string.
-
errline
-
The fourth parameter is optional, errline
,
which contains the line number the error was raised at, as an integer.
-
errcontext
-
The fifth parameter is optional, errcontext
,
which is an array that points to the active symbol table at the point
the error occurred. In other words, errcontext
will contain an array of every variable that existed in the scope the
error was triggered in.
User error handler must not modify error context.
If the function returns FALSE then the normal error handler continues.
-
error_types
-
Can be used to mask the triggering of the
error_handler
function just like the error_reporting ini setting
controls which errors are shown. Without this mask set the
error_handler
will be called for every error
regardless to the setting of the error_reporting setting.
Return Values
Returns a string containing the previously defined
error handler (if any), or NULL on error. If the previous handler
was a class method, this function will return an indexed array with
the class and the method name.
Examples
Example #1 Error handling with set_error_handler() and trigger_error()
The example below shows the handling of internal exceptions by
triggering errors and handling them with a user defined function:
<?php
// error handler function
function myErrorHandler($errno, $errstr, $errfile, $errline)
{
switch ($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 />
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