How to handle error log files in php

During the PHP development process, error log files can not only help developers quickly locate code problems, but also help maintainers troubleshoot problems. Therefore, error log files need to be recorded in the project.

There are many specific solutions for recording error log files. This article will introduce PHP’s error handling function.

1. Set error level

In PHP, you can control which types of errors are recorded in the log file by setting the error level. This can be set in code using the error_reporting() function or in the php.ini file. The error levels in PHP mainly include the following:

1.1 E_ERROR, fatal error, such as file or constant not found, etc., the program terminates;

1.2 E_WARNING, warning error, such as the number of parameters Incorrect or function returns wrong value, etc., can be ignored;

1.3 E_PARSE, parsing error, such as syntax error, etc., the program terminates;

1.4 E_NOTICE, notification error, such as undefined access variables, etc., can be ignored;

1.5 E_STRICT, suggested errors, such as using outdated functions, can be ignored.

According to project requirements, different error levels can be set according to specific situations.

2. Using PHP error handling functions

PHP provides the set_error_handler() function for setting custom error handling functions. Set the error handling function through this function. When an error occurs, the corresponding processing function will be automatically triggered and the error information will be passed to the processing function. Developers can obtain error information through the processing function and log the error information to the error log file.

The following is a simple sample code:

function errorHandler($errno, $errmsg, $errfile, $errline) {
    $log = '[' . date('Y-m-d H:i:s') . '] ' . $errmsg . ' in file ' . $errfile . ' on line ' . $errline . PHP_EOL;
    error_log($log, 3, '/your/path/error.log');
}

set_error_handler('errorHandler');

In the above code, a custom error handling function errorHandler() is set through the set_error_handler() function. When an error occurs, PHP calls the errorHandler() function, passing it four parameters: error number, error message, error file, and error line number. Organize the error log text in the errorHandler() function and write it to the specified log file using the error_log() function. The second parameter of the error_log() function (here 3) indicates writing the error log to a file, and the third parameter is the specified error log file path.

3. Error log optimization

When recording error log files, some optimizations can also be made to better meet project needs.

3.1 Use try-catch block

Using try-catch block in code can effectively capture error information during program running and handle it accordingly.

try {
    // 代码块
} catch (Exception $e) {
    // 异常处理逻辑
}

When an error occurs in the code block, an exception will be thrown and entered into the catch block. Error information can be logged to the error log file in the catch block.

3.2 Recording the error stack

If the project’s error log file needs to record more detailed information, the error stack information can be recorded together. The debug_backtrace() function is provided in PHP to obtain detailed information about the current error.

function errorHandler($errno, $errmsg, $errfile, $errline) {
    $stack = debug_backtrace();
    $log = '[' . date('Y-m-d H:i:s') . '] ' . $errmsg . ' in file ' . $errfile . ' on line ' . $errline . PHP_EOL;
    foreach ($stack as $i => $trace) {
        if ($i == 0) {
            continue;
        }
        $log .= '#' . $i . ' ' . $trace['file'] . '(' . $trace['line'] . '): ';
        if (isset($trace['class'])) {
            $log .= $trace['class'] . '->';
        }
        $log .= $trace['function'] . '()' . PHP_EOL;
    }
    error_log($log, 3, '/your/path/error.log');
}

In the above code, the stack information of the current error is obtained by calling the debug_backtrace() function and recorded in the error log file.

Summary

Recording error log files in PHP projects is very helpful for both code development and maintenance. This article introduces how to record error log files through PHP's error handling function, and briefly introduces some optimization points when recording error log files. Developers can choose a suitable solution to record error log files based on their project needs.

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