How to do error handling in PHP?

PHP is a commonly used programming language, especially suitable for web development. Developers will inevitably encounter various errors and exceptions when writing code. A good error handling mechanism helps improve the robustness and maintainability of the code and ensures the stability and security of the code. This article will explain how to do error handling in PHP.

1. Error level

There are multiple error levels in PHP. You can control which error information will be recorded and displayed by setting the error level.

• E_ERROR: Fatal error that will cause the script to terminate execution.
• E_WARNING: Non-fatal warning message, the script will continue to execute.
• E_NOTICE: Provides a warning message for situations that may cause problems, and the script will continue to execute.
• E_STRICT: Provides warning information on compatibility and standardization for code quality improvement.
• E_DEPRECATED: Provides warning information about deprecated and future removal of functionality.

In order to control these error levels, you can use the error_reporting() function. For example, the following code is set to output only E_ERROR and E_WARNING level error messages:

<?php
error_reporting(E_ERROR | E_WARNING);
?>

2. Error handling function

PHP provides a series of functions to handle different types of errors information. These functions will be set as error handling functions to handle the corresponding error levels.

• set_error_handler(): Set a custom error handling function.
• set_exception_handler(): Set a custom exception handling function.
• register_shutdown_function(): Register a function that will be automatically called when the script execution is completed.

The following is some sample code to show how to implement a custom error handling function:

<?php
function custom_errorhandler($errno, $errstr, $errfile, $errline) {
    echo "Error: [$errno] $errstr - $errfile:$errline";
}

set_error_handler("custom_errorhandler");

// 以下代码会产生一个错误
$test = 2 / 0;
?>

The above code will output:

Error: [2] Division by zero - /var/www/example.php:7

Error_handler() is customized here Function, which is called when an error occurs during script execution.

3. Exception handling

Exceptions are also supported in PHP, and exception handling can be achieved through the try, catch and throw keywords.

The code in the try block may throw an exception. If the code in the try block throws an exception, the rest of the code in the block will not be executed, but will immediately jump to the catch block. The catch block will try to catch the thrown exception and handle it accordingly.

If no exception is caught, execution of the code after the catch block continues.

The following is a sample code for simple exception handling:

<?php
function divide($a, $b) {
    if ($b == 0) {
        throw new Exception('Cannot divide by zero');
    } else {
        return $a / $b;
    }
}

try {
    echo divide(2, 0);
} catch (Exception $e) {
    echo 'Caught exception: ', $e->getMessage();
}
?>

Output:

Caught exception: Cannot divide by zero

In the above code, an exception is thrown from the divide() function. The divide() function is called in the try code block. Because the input $b=0, an exception is thrown. Catch the exception in the catch code block and output the information.

4. Logging

In order to better track and troubleshoot errors, logging application logs is an important part. You can use PHP's built-in function error_log() to record error information to a file. The code is as follows:

<?php
function custom_errorhandler($errno, $errstr, $errfile, $errline) {
    $log_message = "Error: [$errno] $errstr - $errfile:$errline";
    error_log($log_message, 3, "error.log");
}

set_error_handler("custom_errorhandler");

// 以下代码会产生一个错误
$test = 2 / 0;
?>

The above code will record error information to the error.log file.

5. Conclusion

Error handling is a very important part of any programming language. PHP provides a variety of ways to handle errors, including setting error levels, setting custom error handling functions, using exception handling and logging, etc. Correctly handling errors can improve the stability, robustness and maintainability of the code, ensuring the reliability and security of the application.

The above is the detailed content of How to do error handling in PHP?. For more information, please follow other related articles on the PHP Chinese website!