PHP error handling function implements program exception handling function

PHP error handling function implements the function of handling program exceptions

In the process of developing a program, various exceptions will inevitably occur, such as code errors , database connection failure, file reading error, etc. In order to better handle these exceptions, PHP provides a series of error handling functions to enable us to discover and handle problems in the program in a timely manner.

1. The role of the error handling function

The role of the error handling function is to capture and handle errors that occur in the program to prevent the program from exiting directly or displaying unfriendly error messages to the user. By using these error handling functions, we can take appropriate measures when an error occurs, such as logging error information, sending error reports, displaying a friendly user interface, etc.

2. Commonly used error handling functions

1. error_reporting()

error_reporting() The function is used to set the current script to be able to The error level reported. This function accepts a parameter that specifies the error level to report.

Commonly used error levels include:

• E_ALL: Report all errors and warnings
• E_ERROR: Report fatal Error
• E_WARNING: Reporting a non-fatal runtime warning
• E_NOTICE: Reporting a runtime notification

2. set_error_handler()

set_error_handler() The function is used to customize the error handling function. When an error occurs, PHP calls a custom error handling function to handle the error.

The format of a custom error handling function is usually as follows:

function custom_error_handler($error_number, $error_message, $error_file, $error_line) {
  // 处理错误的逻辑代码
}

Among them, $error_number represents the level of the error, $error_message represents the specific error Content, $error_file represents the file name where the error is located, error_line represents the line number where the error is located.

3. trigger_error()

trigger_error() The function is used to manually trigger an error message. It accepts a parameter that specifies the error message to trigger.

Commonly used triggers include:

• E_USER_ERROR: Fatal user-generated error
• E_USER_WARNING: User Generated Warning
• E_USER_NOTICE: User Generated Tip

4. error_log()

error_log( ) function is used to log error messages to the specified log file. It accepts three parameters, which are error message, log type and log file name.

Commonly used log types include:

• 0: Error messages are written to the server error log file
• 1: The error message is sent to the PHP system log
• 3: The error message is written to the specified file

3. Example of using the error handling function

The following is a simple example that demonstrates how to use error handling functions to catch and handle exceptions in your program.

// 设置报告的错误级别
error_reporting(E_ALL);

// 自定义错误处理函数
function custom_error_handler($error_number, $error_message, $error_file, $error_line) {
  // 记录错误信息到日志文件
  error_log("Error: [$error_number] $error_message in $error_file on line $error_line", 3, "error.log");
  
  // 发送错误报告给管理员
  mail("admin@example.com", "程序出错啦！", "错误信息：$error_message");
  
  // 显示友好的错误界面
  echo "抱歉，程序遇到了一些问题，请稍后再试！";
}

// 设置自定义的错误处理函数
set_error_handler("custom_error_handler");

// 触发一个致命错误
trigger_error("这是一个致命错误！", E_USER_ERROR);

// 触发一个警告
trigger_error("这是一个警告！", E_USER_WARNING);

// 触发一个提示
trigger_error("这是一个提示！", E_USER_NOTICE);

In the above code, first use error_reporting() to set the reported error level to E_ALL, and then define a custom error handling functioncustom_error_handler(), this function will record the error information to the log file, send it to the administrator via email, and finally display a friendly error interface.

At the end of the code, we triggered a fatal error, a warning and a prompt through trigger_error() to verify whether our error handling function took effect.

Summary:

PHP’s error handling function provides us with a powerful tool for handling program exceptions and plays an important role in the development process. By properly using error handling functions, we can better capture and handle errors in the program and improve the stability and reliability of the program. Therefore, we should be proficient in the use of error handling functions and apply them to our projects to ensure the normal operation of the program.

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