Application of PHP functions in logging

PHP logging function: error_log(): Log messages to the specified destination, such as a file or system log. syslog(): records messages to the system log and supports specifying message priority. Log level: PHP supports multiple log levels, which can classify logs according to the importance of the message. Additional tip: Use use_log_errors to log PHP errors and warnings. Extend functionality using third-party logging libraries. Implement log rotation to avoid excessively large log files.

Application of PHP functions in logging

Logging is crucial to the development and maintenance of applications, it can Help us track application behavior, debug issues, and troubleshoot. PHP provides many useful functions that simplify the logging process.

Use the error_log() function

error_log() The function logs the message to the specified destination (such as a file or system log). The basic syntax is as follows:

error_log($message, $message_type, $destination, $extra_headers);

• $message: The message to be logged.
• $message_type: Message type (e.g. E_USER_NOTICE).
• $destination: The destination for logging (e.g. error_log.txt).
• $extra_headers: Custom header information appended to the log message.

Practical case: Recording user login attempts

We can use the error_log() function to record user attempts to log in to the application:

<?php
if (isset($_POST['username']) && isset($_POST['password'])) {
    $username = $_POST['username'];
    $password = $_POST['password'];

    // 检查登录凭证
    if (authenticate($username, $password)) {
        // 登录成功，此处省略其他操作
    } else {
        // 登录失败，记录尝试
        $message = "登录失败，用户：$username";
        error_log($message, 0, "login_attempts.log");
    }
}
?>

Use the syslog() function

syslog() function to log messages to the system log. The basic syntax is as follows:

syslog($priority, $message);

• $priority: message priority (for example, LOG_INFO).
• $message: The message to be logged.

Practical case: Recording application startup

We can use the syslog() function to record application startup:

<?php
syslog(LOG_INFO, "应用程序启动");
?>

Using log levels

PHP logging functions support multiple log levels, allowing us to classify logs according to the importance of the message. Commonly used log levels include:

• LOG_EMERGENCY: Emergency message
• LOG_ALERT: Alert message
• LOG_CRITICAL: Critical error
• LOG_ERROR: Error message
• LOG_WARNING: Warning message
• LOG_NOTICE: Notification message
• LOG_INFO: Information message
• LOG_DEBUG: Debug message

Others Tip

• Use the use_log_errors option to log PHP errors and warnings to a log file.
• Use third-party logging libraries such as monolog or psr/log to extend PHP’s logging capabilities.
• Implement a log rotation policy to avoid log files becoming too large.

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