实例化PHP类的更好方法

Question

I have a class with only one function:

<?php

class EventLog
{

    public function logEvent($data, $object, $operation, $id)
    {
        //Log it to a file...
        $currentTime = new DateTime();
        $time = $currentTime->format('Y-m-d H:i:s');

        $logFile = "/.../event_log.txt";
        $message = "Hello world";

        //Send the data to a file...
        file_put_contents($logFile, $message, FILE_APPEND);
    }

}

Then I have another class with many functions and each and everyone need to call the above method. To instantiate the class in every function I have done:

$log = new EventLog();
//Then...
$log->logEvent($data, $object, $operation, $id);

The problem: I have used the above code in every function and what I would like to know is if there is a way to instantiate the EventLog class once for all the functions that need it.

Answer 1

You can create single instance at the beginning(for example) of your script and inject it into constructors of those classes that need it. This is called Dependency Injection. Most PHP web frameworks utilize this principle.

class Logger
{
   public function writeToLogFile(){
   ...
   }
}


class DoSomethingUseful
{
     private $logger;
     public function __construct(Logger $logger) //php 7 optional type hinting
     {
          $this->logger = $logger;
     }

     public function actualWork()
     {
          //do work
          $this->logger->writeToLogFile('whatever');
     }
}

class Application
{
     public function setUp()
     {
         //create database connection, other stuff
         $this->logger = new Logger;
     }

     public function work()
     {
         $action = new DoSomethingUseful($this->logger);
         $action->actualWork();

     }
}

Answer 2

You could also try using PHP Trait (with namespacing):

<?php
namespace App\Traits;

trait EventLog
{

    public function logEvent($data, $object, $operation, $id)
    {
        //Log it to a file...
        $currentTime = new DateTime();
        $time = $currentTime->format('Y-m-d H:i:s');

        $logFile = "/.../event_log.txt";
        $message = "Hello world";

        //Send the data to a file...
        file_put_contents($logFile, $message, FILE_APPEND);
    }

}

In your other class:

<?php
namespace App;

// import your trait here
use App\Traits\EventLog;

class OtherClass
{
    use EventLog;

    public function sample() {
        // sample call to log event
        $this->logEvent($data, $object, $operation, $id);
    }

}