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Building a basic file loader class - PHP

Loading sources on the fly is one of the most common tasks that PHP programmers have to tackle during the development of web applications. This typical situation must be faced independently of the scale of the programs being created. This means a loader mechanism must be developed. Keep reading as we take a close look at these mechanisms in this eight-part article series.

TABLE OF CONTENTS:
  1. Building Loader Apps in PHP
  2. Start building loading programs with a require_once() function
  3. Building a basic file loader class
  4. The loader class in action
By: Alejandro Gervasio
Rating: starstarstarstarstar / 6
May 27, 2009

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As I stated previously, developing a file loading system that abstracts the load process a bit further is a straightforward procedure that can be tackled with minimal efforts. Basically, this system will base its functionality on a simple loader class that will behave as a proxy for a “require_once()” function. 

Imagine now that there are a couple of files that need to be included by a certain PHP application, whose definitions are as follows:

('sample_file1.php')

 

<?php

echo ' This file has been loaded with the Loader class.' . '<br />';

?>

 

 

('sample_file2.php')

<?php

echo 'This file has been loaded at the following time: ' . date('H:i:s');

?>

Again, it’s fair to say that I’m not going to waste your time (and mine) discussing how the above files do their things. Instead, pay close attention to the signature of the file loading class below, which not surprisingly has been called “Loader().” It looks like this:

class Loader

{

// constructor (not implemented)

public function __construct(){}

 

// load specified file

public function load($filepath)

{

if (!file_exists($filepath) OR is_dir($filepath))

{

throw new Exception('The specified file cannot be found!');

}

require_once($filepath);

}

}

Despite its rather basic definition, the previous “Loader()” class is a considerable breakthrough when it comes to building a file loading mechanism. It not only acts like a wrapper for the “require_once()” function, but it handles the eventual errors that might occur during the load process in a more elegant way, through native PHP exceptions.

At this point, everything is starting to look a bit better. I created a basic loader class, and there are a couple of sample files that need to be included within a fictional application to display some trivial messages on screen.

The question that comes up now is: how can these two files be loaded by the previous “Loader” class? Well, it’s quite possible that you’ve already found the answer, but in the last section of this tutorial I’m going to create a hands-on example that will demonstrate how to use this class in a few simple steps.

To learn more about how this example will be developed, go ahead and read the next segment.



 
 
>>> More PHP Articles          >>> More By Alejandro Gervasio
 

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