Examples

Below we can see an example of using the error handling capabilities in PHP. We define an error handling function which logs the information into a file (using an XML format), and e-mails the developer if a critical error in the logic happens.

Example #1 Using error handling in a script

<?php
// we will do our own error handling
error_reporting(0);

// user defined error handling function
function userErrorHandler($errno, $errmsg, $filename, $linenum, $vars)
{
// timestamp for the error entry
$dt = date("Y-m-d H:i:s (T)");

// define an assoc array of error string
// in reality the only entries we should
// consider are E_WARNING, E_NOTICE, E_USER_ERROR,
// E_USER_WARNING and E_USER_NOTICE
$errortype = array (
E_ERROR => 'Error',
E_WARNING => 'Warning',
E_PARSE => 'Parsing Error',
E_NOTICE => 'Notice',
E_CORE_ERROR => 'Core Error',
E_CORE_WARNING => 'Core Warning',
E_COMPILE_ERROR => 'Compile Error',
E_COMPILE_WARNING => 'Compile Warning',
E_USER_ERROR => 'User Error',
E_USER_WARNING => 'User Warning',
E_USER_NOTICE => 'User Notice',
E_STRICT => 'Runtime Notice',
E_RECOVERABLE_ERROR => 'Catchable Fatal Error'
);
// set of errors for which a var trace will be saved
$user_errors = array(E_USER_ERROR, E_USER_WARNING, E_USER_NOTICE);

$err = "<errorentry>\n";
$err .= "\t<datetime>" . $dt . "</datetime>\n";
$err .= "\t<errornum>" . $errno . "</errornum>\n";
$err .= "\t<errortype>" . $errortype[$errno] . "</errortype>\n";
$err .= "\t<errormsg>" . $errmsg . "</errormsg>\n";
$err .= "\t<scriptname>" . $filename . "</scriptname>\n";
$err .= "\t<scriptlinenum>" . $linenum . "</scriptlinenum>\n";

if (
in_array($errno, $user_errors)) {
$err .= "\t<vartrace>" . wddx_serialize_value($vars, "Variables") . "</vartrace>\n";
}
$err .= "</errorentry>\n\n";

// for testing
// echo $err;

// save to the error log, and e-mail me if there is a critical user error
error_log($err, 3, "/usr/local/php4/error.log");
if (
$errno == E_USER_ERROR) {
mail("phpdev@example.com", "Critical User Error", $err);
}
}


function
distance($vect1, $vect2)
{
if (!
is_array($vect1) || !is_array($vect2)) {
trigger_error("Incorrect parameters, arrays expected", E_USER_ERROR);
return
NULL;
}

if (
count($vect1) != count($vect2)) {
trigger_error("Vectors need to be of the same size", E_USER_ERROR);
return
NULL;
}

for (
$i=0; $i<count($vect1); $i++) {
$c1 = $vect1[$i]; $c2 = $vect2[$i];
$d = 0.0;
if (!
is_numeric($c1)) {
trigger_error("Coordinate $i in vector 1 is not a number, using zero",
E_USER_WARNING);
$c1 = 0.0;
}
if (!
is_numeric($c2)) {
trigger_error("Coordinate $i in vector 2 is not a number, using zero",
E_USER_WARNING);
$c2 = 0.0;
}
$d += $c2*$c2 - $c1*$c1;
}
return
sqrt($d);
}

$old_error_handler = set_error_handler("userErrorHandler");

// undefined constant, generates a warning
$t = I_AM_NOT_DEFINED;

// define some "vectors"
$a = array(2, 3, "foo");
$b = array(5.5, 4.3, -1.6);
$c = array(1, -3);

// generate a user error
$t1 = distance($c, $b) . "\n";

// generate another user error
$t2 = distance($b, "i am not an array") . "\n";

// generate a warning
$t3 = distance($a, $b) . "\n";

?>

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User Contributed Notes 1 note

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-1
delcroixenator at gmail dot com
10 months ago
For the above "distance" function to work properly, you must correct it as follows:
$d = 0.0; // must be moved before the for loop
$d += $c2*$c2 - $c1*$c1; // must be replaced by $d += ($c2 - $c1) ** 2 ;

Another thing: in the "userErrorHandler" function, the variables $vars and $user_errors are declared but not used.
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