Error handling for beginners in PHP

PHP Error Handling

In PHP, the default error handling is simple. An error message is sent to the browser with the file name, line number, and a message describing the error.

#Error handling is an important part when creating scripts and web applications. If your code lacks error detection coding, the program will look unprofessional and open the door to security risks.

This tutorial introduces some of the most important error detection methods in PHP.

We will explain different error handling methods for you:

Simple "die()" statement

Custom errors and error triggers

Error reporting

Basic error handling: using the die() function

The first example shows a simple script that opens a text file:

$file=fopen("welcome.txt","r");
?>

If the file does not exist, you You will get an error similar to this:

Warning: fopen(welcome.txt) [function.fopen]: failed to open stream:
No such file or directory in /www/php/test/test. php on line 2

In order to avoid users getting error messages similar to the above, we check whether the file exists before accessing it:

Now if the file does not exist, it will be output directly File does not exist

Create custom error handler

Creating a custom error handler is very simple. We simply created a dedicated function that can be called when an error occurs in PHP.

The function must be able to handle at least two parameters (error level and error message), but can accept up to five parameters (optional: file, line-number and error context):

Syntax

##error_function(error_level,error_message,

error_file,error_line,error_context)

error_level Required. Specifies the error reporting level for user-defined errors. Must be a number. See the table below: Error reporting levels.

error_message Required. Specifies error messages for user-defined errors.

error_file Optional. Specifies the file name where the error occurred.

error_line Optional. Specifies the line number where the error occurred.

error_context Optional. Specifies an array containing each variable in use when the error occurred and their values.

Error reporting levels

These error reporting levels are different types of errors handled by user-defined error handlers:

2 E_WARNING Non-fatal run-time error. Do not pause script execution.

8 E_NOTICE run-time notification. Occurs when the script finds a possible error, but can also occur when the script is running normally.

256 E_USER_ERROR Fatal user-generated error. This is similar to E_ERROR set by the programmer using the PHP function trigger_error().

512 E_USER_WARNING Non-fatal user-generated warning. This is similar to the E_WARNING set by the programmer using the PHP function trigger_error().

1024 E_USER_NOTICE User-generated notifications. This is similar to E_NOTICE set by the programmer using the PHP function trigger_error().

4096 E_RECOVERABLE_ERROR Catchable fatal error. Like E_ERROR, but can be caught by a user-defined handler. (See set_error_handler())

8191 E_ALL All errors and warnings. (In PHP 5.4, E_STRICT becomes part of E_ALL)

Create a function that handles errors

Error: [$errno] $errstr
"; echo "脚本结束"; die(); } ?>

The above code is a simple Error handling function. When it is triggered, it gets the error level and error message. It then prints the error level and message, and terminates the script.

Now that we have created an error handling function, we need to determine when to trigger the function

Set up the error handler

PHP's default error handler is the built-in error handler. We are going to transform the above function into the default error handler when the script is running.

You can modify the error handler so that it only applies to certain errors, so that the script can handle different errors in different ways. However, in this case we are going to use our custom error handler for all errors

set_error_handler("customError");