How to implement language packs in PHP - php

Question

I created 3 language packs for my site: English, Spanish and French. I am just having trouble implementing them based on user selection. I have the following drop down menu:
<select onchange='document.location.href=this.options[this.selectedIndex].value;'>
<option>Select</option>
<option value="?lang=eng">US English</option>
<option value="?lang=esp">Español</option>
<option value="?lang=fra">Français</option>
</select>
How can I include the language files based on what the user selects, I just don't know what to put as the condition in the if statement.
Thanks.

Answer 1

As you're bringing in the option via a query string, you can access it with
$lang = $_GET['lang']

Answer 2

At first, save the value that the user selected in the user session. e.g.:
switch($_POST['lang']) {
case 'en': $_SESSION['lang'] = 'English'; break;
case 'sp': $_SESSION['lang'] = 'Spanish'; break;
default: $_SESSION['lang'] = 'English'; break;
}
On every page request, fetch the language files from the relevant language folder according to the value the you saved.
For example, this how will look the files structure:
English
Global.php
Register.php
Spanish
Global.php
Register.php
Then, whenever you need to load a text file, use:
function load_text_file($filename) {
include 'languages/' . $_SESSION['lang'] . '/' . $filename.'php';
return $txt; // $txt should be an array
}
//...
$text = array();
$text += load_text_file('Global');
$text += load_text_file('Register');

Answer 3

For my template, that piece of code is
$_SESSION['language'] = 'english';