How to capture system error messages in PHP

In PHP development, we often encounter various errors, including syntax errors, runtime errors, logic errors, etc. How to capture error information quickly and accurately is one of the important skills that need to be mastered during the development process. This article will introduce how to capture system error information in PHP.

1. Error types

1. Syntax error

A syntax error refers to the incorrect syntax rules when writing code. When the PHP compiler detects this error It will directly stop executing the program and give an error message.

2. Runtime error

A runtime error refers to an error that occurs during program execution, but does not interrupt the execution of the program. This error is generally caused by calling the wrong function or variable, assigning the wrong type or value, etc.

3. Serious errors

Serious errors refer to those errors that cause the program to crash or be unable to continue execution, such as insufficient memory, etc.

2. Error handling functions

PHP provides many error handling functions that can capture and process error information during program execution. The following are several commonly used error handling functions:

1.set_error_handler()

The set_error_handler() function is used to customize the error handling function. This function must be called before the error occurs, otherwise the custom function will not be called.

For example, we can define a custom function to handle runtime errors:

function myErrorHandler($errno, $errstr, $errfile, $errline)
{
    echo "<b>错误：</b> [$errno] $errstr<br>";
    echo "错误所在行：$errline<br>";
    echo "错误所在文件：$errfile<br>";
    echo "PHP版本：" . phpversion();
}

set_error_handler("myErrorHandler");

2.set_exception_handler()

The set_exception_handler() function is used to customize the exception handling function . Exceptions refer to errors that occur during program execution. When an exception occurs in the program, PHP will stop execution and jump to the exception handling function.

For example, we can define a custom function that handles exceptions:

function myExceptionHandler($exception)
{
    echo "<b>异常信息：</b>" . $exception->getMessage() . "<br>";
    echo "<b>异常所在文件：</b>" . $exception->getFile() . "<br>";
    echo "<b>异常所在行：</b>" . $exception->getLine() . "<br>";
    echo "<b>异常堆栈：</b><pre class="brush:php;toolbar:false">" . $exception->getTraceAsString() . "

"; } set_exception_handler("myExceptionHandler");

3.error_reporting()

The error_reporting() function is used to set the reported error level. When we are debugging the code, we can set the error level to E_ALL, so that all error messages can be output. If you want to turn off error reporting, you can set it to 0.

For example:

error_reporting(E_ALL); //输出所有错误
error_reporting(0); //关闭错误报告

3. Capture and output error information

In PHP, we can use the try-catch statement to capture and process exception information, and we can also use The error_log() function records error information to the log file.

1. Capture exception information

We can use the try-catch statement in the program to capture exception information, and then output or record it to a log file.

For example:

try {
    //执行代码
} catch (Exception $e) {
    echo "发生异常：" . $e->getMessage();
}

2. Record error information to the log file

We can use the error_log() function to record the error information to the log file, which will help us Quickly find and locate errors.

For example:

try {
    //执行代码
} catch (Exception $e) {
    error_log("发生异常：" . $e->getMessage(), 3, "error.log");
}

The first parameter of the error_log() function is the error information that needs to be recorded, the second parameter is the way to record the log file, 3 means writing the error information to In the file, the third parameter is the log file name.

4. Summary

In PHP development, capturing and processing system error information is a very important skill. By using the error handling function, exception handling function, try-catch statement and error_log() function provided by PHP, error information can be captured and processed more quickly and conveniently, improving the maintainability and stability of the code.

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