Error Handing in PHP

Here are some of the Error Handling Techniques

It is important to configure PHP's error reporting settings depending on which phase of development the web application is currently in. Generally, the programmer wants to see all warnings and errors in the web browser during the initial phase of development, and later, once the site has launched, send error messages to a log file so that visitors do not see them.
Error Reporting for Development

During development, you want to display all errors and warnings to the browser.

// Report all PHP errors
ini_set('error_reporting', E_ALL);

// Set the display_errors directive to On
ini_set('display_errors', 1);

Error Reporting for Production

In production, you may want to lower the error reporting level and not display errors to the browser.

// Report simple running errors
ini_set('error_reporting', E_ALL ^ E_NOTICE);

// Set the display_errors directive to Off
ini_set('display_errors', 0);

// Log errors to the web server's error log
ini_set('log_errors', 1);

Logging errors

You can use the PHP function error_log() to send errors to your own log file or an e-mail address. This is particularly important since most developers on campus do not have access to the web servers logs. Used in conjunction with a custom error handler, error_log() is especially useful.

// Destinations
define("ADMIN_EMAIL", "test@test.com");
define("LOG_FILE", "/error/errors.log");

// Destination types
define("DEST_EMAIL", "1");
define("DEST_LOGFILE", "3");

/* Examples */

// Send an e-mail to the administrator
error_log("Please fix this!", DEST_EMAIL, ADMIN_EMAIL);

// Write the error to our log file
error_log("Error", DEST_LOGFILE, LOG_FILE);

Create a custom error handler

It is possible to override PHP's default mechanism for handling errors. This option gives the programmer full control over what actions to take when an error is raised. Note that since this method completely replaces PHP's native functionality, it is important to pay special care when writing a custom error handler.

// Destinations
define("ADMIN_EMAIL", "test@test.com");
define("LOG_FILE", "/error/errors.log");

// Destination types
define("DEST_EMAIL", "1");
define("DEST_LOGFILE", "3");

/**
* my_error_handler($errno, $errstr, $errfile, $errline)
*
* Author(s): thanosb, ddonahue
* Date: May 11, 2008
*
* custom error handler
*
* Parameters:
* $errno: Error level
* $errstr: Error message
* $errfile: File in which the error was raised
* $errline: Line at which the error occurred
*/

function my_error_handler($errno, $errstr, $errfile, $errline)
{
switch ($errno) {
case E_USER_ERROR:
// Send an e-mail to the administrator
error_log("Error: $errstr \n Fatal error on line $errline in file $errfile \n", DEST_EMAIL, ADMIN_EMAIL);

// Write the error to our log file
error_log("Error: $errstr \n Fatal error on line $errline in file $errfile \n", DEST_LOGFILE, LOG_FILE);
break;

case E_USER_WARNING:
// Write the error to our log file
error_log("Warning: $errstr \n in $errfile on line $errline \n", DEST_LOGFILE, LOG_FILE);
break;

case E_USER_NOTICE:
// Write the error to our log file
error_log("Notice: $errstr \n in $errfile on line $errline \n", DEST_LOGFILE, LOG_FILE);
break;

default:
// Write the error to our log file
error_log("Unknown error [#$errno]: $errstr \n in $errfile on line $errline \n", DEST_LOGFILE, LOG_FILE);
break;
}

// Don't execute PHP's internal error handler
return TRUE;
}


// Use set_error_handler() to tell PHP to use our method
$old_error_handler = set_error_handler("my_error_handler");

Error Report levels

These error report levels are the different types of error the user-defined error handler can be used for:
Value Constant Description
2 E_WARNING Non-fatal run-time errors. Execution of the script is not halted
8 E_NOTICE Run-time notices. The script found something that might be an error, but could also happen when running a script normally
256 E_USER_ERROR Fatal user-generated error. This is like an E_ERROR set by the programmer using the PHP function trigger_error()
512 E_USER_WARNING Non-fatal user-generated warning. This is like an E_WARNING set by the programmer using the PHP function trigger_error()
1024 E_USER_NOTICE User-generated notice. This is like an E_NOTICE set by the programmer using the PHP function trigger_error()
4096 E_RECOVERABLE_ERROR Catchable fatal error. This is like an E_ERROR but can be caught by a user defined handle (see also set_error_handler())
8191 E_ALL All errors and warnings, except level E_STRICT (E_STRICT will be part of E_ALL as of PHP 6.0)