PHP Error Handling - codingtube

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

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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:

(E_ERROR | E_PARSE | E_CORE_ERROR | E_COMPILE_ERROR | E_USER_ERROR)

Table of Error-reporting values

Value	Meaning
E_ERROR	Runtime errors
E_WARNING	Runtime warnings
E_PARSE	Compile-time parse errors
E_NOTICE	Runtime notices
E_CORE_ERROR	Errors generated internally by PHP
E_CORE_WARNING	Warnings generated internally by PHP
E_COMPILE_ERROR	Errors generated internally by the Zend scripting engine
E_COMPILE_WARNING	Warnings generated internally by the Zend scripting engine
E_USER_ERROR	Runtime errors generated by a call to trigger_error()
E_USER_WARNING	Runtime warnings generated by a call to trigger_error()
E_USER_NOTICE	Runtime notices generated by a call to trigger_error()
E_ALL	All of the above options

Table of Error-reporting values

Example of Error handling in PHP

<?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";

?>

Error Reporting in PHP

Table of Error-reporting values

Example of Error handling in PHP

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