php
PHP Error Handling
These are functions dealing with error handling and logging. They allow you to define your own error handling rules, as well as modify the way the errors can be logged.   An error message with filename, line number and a message describing the error is sent to the web browser.

This tutorial contains some of the most common error checking methods in PHP.

We will show different error handling methods:

  • die() statements
  • Custom errors
  • Error reporting
Using die() function

The die() function is used to output an error message when an error is encountered.

The system error message might be big and difficult to understand. This error message is suppressed and the message given in the die() function is displayed.

Let us have an example to demonstrate die() function.

Example :
<!DOCTYPE html>
<html>
<head>
    <title>Error Handling in PHP</title>
</head>
<body>

<?php
	$ftl=fopen("MY_text.txt","r");
?>

</body>
</html>
Output :

To prevent the user from getting an error message like the one above, we test whether the file exist before we try to access it :

<!DOCTYPE html>
<html>
<head>
    <title>Error Handling in PHP</title>
</head>
<body>

<?php
   if(!file_exists("examples/my-file.txt")) {
      die("File not found");
   }else {
      $file = fopen("examples/my-file.txt","r");
      print " This file is Opend sucessfully";
   }
   // Test of the code here.
?>

</body>
</html>
Output :
Creation of custom error handler

We can use die() to handle errors, but we can make the error messages more creative just like the system error messages by providing the type of error, error message, file in which the error occurred by defining a error function.

This function can have in total 5 parameters of which 2 are basic and mandatory and the other 3 are optional.

This function must be able to handle a minimum of two parameters (error level and error message) but can accept up to five parameters (optionally: file, line-number, and the error context):

Syntax

error_function(error_level,error_message,error_file,error_line,error_context);

Parameter Description
error_level Required - Specifies the error report level for the user-defined error. Must be a value number.
error_message Required - Specifies the error message for the user-defined error
error_file Optional - Specifies the file name in which the error occurred
error_line Optional - Specifies the line number in which the error occurred
error_context Optional - Specifies an array containing every variable and their values in use when the error occurred
Error report levels

These error report levels are the different types of error the user-defined error handler can be used for.

Constant Description Value
E_ERROR Execution of the script comes to a halt. An example is memory allocation problem. 1
E_WARNING Execution of the script is not halted, warnings generated.  2
E_PARSE  Parse errors generated by parsers during compilation. 4
E_NOTICE  Run-time notices which indicated that may be an error took place but may also be a normal course of action. 8
E_CORE_ERROR Fatal errors that occur during the initial startup of PHP. 16
E_CORE_WARNING Warnings (execution of the script is not halted) that occur during PHP's initial startup. 32
E_COMPILE_ERROR   Fatal compile-time errors. 64
E_COMPILE_WARNING   Compile-time warnings, execution of the script is not halted. 128
E_USER_ERROR   User-generated error message.  256
E_USER_WARNING User-generated warning message.  512
E_USER_NOTICE Same as E_NOTICE. The only difference is, trigger_error() function is used here to generate the error message. 1024 
E_STRICT  User-generated notice message. 2048
E_RECOVERABLE_ERROR  Catchable fatal error. 4096
E_DEPRECATED  Run-time notices.  8192
E_USER_DEPRECATED  User-generated warning message. 16384
E_ALL  All errors and warnings, as supported. Exception level E_STRICT. 30719

All the above error level can be set using following PHP built-in library function where level cab be any of the value defined in above table.

To prevent the user from getting an error message like the one above, we test whether the file exist before we try to access it :

<?php
  function cus_Error_handler($error_no, $error_str) {
  echo "<b>Error:</b> [$error_no] $error_str<br>";
  echo "Ending Script";
  die();
}
?>
Set Error Handler
The default error handler for PHP is the built in error handler. We are going to make the function above the default error handler for the duration of the script.
Syntax

set_error_handler("cus_Error_handler");

<!DOCTYPE html>
<html>
<head>
    <title>Error Handler</title>
</head>
<body>

<?php
	//error handler function
	 function cus_Error_handler($error_no, $error_str) {
  	  echo "<b>Error:</b> [$error_no] $error_str<br>";
	 }
	
	//set error handler
	set_error_handler("cus_Error_handler");
	
	//trigger error
	echo($my_test);
?>

</body>
</html>
Output :