PHP Error Handling

In PHP we cam show all error using error handling. in PHP Error handling is an important part of any real-world application. PHP provides a number of mechanisms that you can use to handle errors, both during the development process and once your application is in a production environment

Error Reporting in PHP

In PHP By default, all conditions except runtime notices are caught and displayed to the user. You can change this behavior globally in your php.ini file with the error_reporting option. You can also locally change the error-reporting behavior in a script using the error_reporting() function

With both the error_reporting option and the error_reporting() function, you specify the conditions that are caught and displayed by using the various bitwise operators to combine different constant values

For example, this indicates all error-level options:


Table of Error-reporting values

E_ERRORRuntime errors
E_WARNINGRuntime warnings
E_PARSECompile-time parse errors
E_NOTICERuntime notices
E_CORE_ERRORErrors generated internally by PHP
E_CORE_WARNINGWarnings generated internally by PHP
E_COMPILE_ERRORErrors generated internally by the Zend scripting engine
E_COMPILE_WARNINGWarnings generated internally by the Zend scripting engine
E_USER_ERRORRuntime errors generated by a call to trigger_error()
E_USER_WARNINGRuntime warnings generated by a call to trigger_error()
E_USER_NOTICERuntime notices generated by a call to trigger_error()
E_ALLAll of the above options
Table of Error-reporting values

Example of Error handling in PHP

// we will do our own error handling

// 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,
    $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("[email protected]", "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", 
            $c1 = 0.0;
        if (!is_numeric($c2)) {
            trigger_error("Coordinate $i in vector 2 is not a number, using zero", 
            $c2 = 0.0;
        $d += $c2*$c2 - $c1*$c1;
    return sqrt($d);

$old_error_handler = set_error_handler("userErrorHandler");

// undefined constant, generates a warning

// 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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