Slide 5.12: PHP errors (cont.)

PHP Errors (Cont.)

Creating a Custom Error Handler
A custom error handler creates a special function that can be called when an error occurs in PHP. This example checks whether the given URL starts with the “http://.” It uses the following functions:

The functions strncmp compares two strings and header sends a raw HTTP header to a client.

The function trigger_error is used to trigger an error message at a user-specified condition.

The function set_error_handler sets a user-defined function to handle errors. It needs one parameter and a second parameter could be added to specify an error level as below.

 <html><body>
 <?php
   // Error handler function 
   function customError( $errno, $errstr ) { 
     echo "<b>Error:</b> [$errno] $errstr<br />";
     echo "Ending Script";
     die( );
   }
 
   // Set error handler 
   set_error_handler( "customError", E_USER_WARNING );
 
   // Trigger error
   $URL = "";
   if ( strncmp( $URL, "http://", 7 ) == 0 ) 
     header( "Location: $URL" );
   else
     trigger_error( "The URL must start with 'http://'", E_USER_WARNING );
 ?>
 </body></html>

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_NOTIC` 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.
`8191`	`E_ALL`	All errors and warnings, except level `E_STRICT`.