Log function of PHP function

Log function of PHP function

When developing PHP applications, we usually encounter many situations that require logging. For example, logging is particularly important when we need to debug a program, troubleshoot problems, or track user behavior. In PHP, the best practice for logging is to use the log function. This article will introduce how to record logs, how to extend, use and configure log functions.

1. Introduction to log functions

In PHP, the system provides log functions, and we can use these functions to record logs. PHP's log functions include:

1. error_log(): used to record error information.
2. syslog(): used to write messages to the system log.
3. openlog(): used to open a log connection in the system.
4. closelog(): used to close the log connection.
5. syslog-ng: Used to record system logs, provide configuration management tools, and support sending logs through multiple protocols such as TCP/IP, UDP, TCP, and SSL.

In practical applications, we usually use the error_log() function for logging.

2. Use the error_log() function to record logs

The basic syntax of the error_log() function is as follows:

bool error_log ( string $message [, int $message_type [, string $destination [, string $extra_headers ]]] )

Among them:

$message: To write Messages entered into the log.

$message_type: Can be the following three types:

• 0: Default value, writes the message to the PHP error log.
• 1: Send the message to the specified file or email address.
• 2: Write the message to the system internal log.

$destination: When $message_type is 1, this parameter specifies the destination file or email address for sending the message; when $message_type is 0, this parameter is ignored; when $message_type is 2 , this parameter specifies the system internal log type.

$extra_headers: When $message_type is 1, this parameter specifies the email header information.

Usually we will record the log in a file, use the following code to write the message to the log file:

$logfile = '/path/to/logfile.log';
error_log($message, 3, $logfile);

This will write $message to the $path/to/logfile.log file middle.

3. Extended log function

PHP provides a function called set_error_handler(), through which we can extend the logging function to make it easier to use and manage logs.

The basic syntax of the set_error_handler() function is as follows:

mixed set_error_handler ( callable $error_handler [, int $error_types = E_ALL | E_STRICT ] )

Among them:

$error_handler: a custom error handling function, which can be a closure or an ordinary function.

$error_types: Optional, the default value is E_ALL | E_STRICT, the error type is specified, only errors of the specified error type will be passed to the $error_handler function for processing.

The sample code is as follows:

$logfile = '/path/to/logfile.log';

function my_error_handler($errno, $errstr, $errfile, $errline) {
    $message = "$errno: $errstr in $errfile on line $errline";
    error_log($message, 3, $logfile);
}

set_error_handler('my_error_handler');

This will write PHP errors to the $path/to/logfile.log file.

4. Use Monolog to extend the log

Another logging method is to use the third-party library Monolog. Monolog is a popular PHP logging library that can easily record various types of logs and provides multiple log transmission and formatting methods.

To use Monolog, you first need to install the Monolog library. The command to install Monolog using Composer is as follows:

composer require monolog/monolog

After the installation is complete, we can use the following code to log:

use MonologLogger;
use MonologHandlerStreamHandler;

$log = new Logger('mylog');
$log->pushHandler(new StreamHandler($logfile, Logger::WARNING));

$log->error('This is an error message.');

This will write the log information to the $path/to/logfile.log file middle.

5. Summary

Logging is one of the basic functions that every application needs to implement. In PHP, we can use the log functions error_log(), syslog(), openlog() and closelog() provided by the system for logging. At the same time, we can also use third-party libraries such as Monolog to extend the logging function. Of course, to implement more customized and complex functions, we can use the set_error_handler() function to customize the way logs are processed to meet our own needs. In actual applications, you should choose the most suitable logging method according to actual needs.

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