The SPL __autoload() method is one of the Magic Methods supplied in PHP. The __autoload method is called whenever a class is instantiated and will load the class the first time it is called. No longer is include(), require, include_once() or require_once needed as the SPL autoload takes care of this internally.

In its simplest form, the SPL autoload class can find all class files in a directory, where the class the class name, matches the file name. This is great for maintaining a naming convention through-out projects.

To instantiate the any other class within the classes directory, the SPL autoload method will load the class definition file without any need to include it.

    /*** nullify any existing autoloads ***/
    spl_autoload_register(null, false);

    /*** specify extensions that may be loaded ***/
    spl_autoload_extensions('.php, .php');

    /*** class_loader ***/
    function class_loader($class)
        $filename = strtolower($class) . '.php';
        $file ='classes/' . $filename;
        if (!file_exists($file))
            return false;
        include $file;

    /*** register the loader functions ***/

But from php version 5.1.2 or greater you can as follow:

class Autoloader {

    static public function loader($class_Name) {
        $className = strtolower($class_Name);
        $filename = path . str_replace('\\', '/', $className) . '.php';
        if (file_exists($filename) && is_readable($filename)) {
            if (class_exists($className)) {
                return true;
        return false;


if (version_compare(PHP_VERSION, '5.1.2', '>=')) {
    //SPL autoloading was introduced in PHP 5.1.2
    if (version_compare(PHP_VERSION, '5.3.0', '>=')) {
        spl_autoload_register('Autoloader::loader', true, true);
    } else {
} else {

     * Fall back to traditional autoload for old PHP versions
     * @param string $classname The name of the class to load
    function __autoload($classname) {
        $className = strtolower($classname);
        $path = path . "{$className}.php";
        if (file_exists($path)) {
        } else {
            die("The file {$classname} could not be found.");


By maintaining this structure, applications and websites developed can save on maintainence when new classes are added, as there is no need to be hunting through code to include them, its all done internally by SP.

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