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set_error_handler

(PHP4 >= 4.0.1)

set_error_handler --  Sets a user-defined error handler function.

Description

string set_error_handler (string error_handler)

Sets a user function (error_handler) to handle errors in a script. Returns the previously defined error handler (if any), or false on error. 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 user function needs to accept 2 parameters: the error code, and a string describing the error. The example below shows the handling of internal execptions 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, $errstr) {
    switch ($errno) {
    case FATAL:
    echo "<b>FATAL</b> [$errno] $errstr<br>\n";
    echo "  Fatal error in line ".__LINE__." of file ".__FILE__;
    echo ", PHP ".PHP_VERSION." (".PHP_OS.")<br>\n";
    echo "Aborting...<br>\n";
    exit -1;
    break;
    case ERROR:
    echo "<b>ERROR</b> [$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 16 of file trigger_error.php, PHP 4.0.1pl2 (Linux)<br>
Aborting...<br>

See also error_reporting(), restore_error_handler(), trigger_error(), user_error()

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