如果你想包含所有在一个目录和它的子目录:

$dir = "classes/";
$dh  = opendir($dir);
$dir_list = array($dir);
while (false !== ($filename = readdir($dh))) {
    if($filename!="."&&$filename!=".."&&is_dir($dir.$filename))
        array_push($dir_list, $dir.$filename."/");
}
foreach ($dir_list as $dir) {
    foreach (glob($dir."*.php") as $filename)
        require_once $filename;
}

不要忘记，它将使用字母顺序来包括您的文件。

下面是我从PHP 5的几个文件夹中包含大量类的方法。但这只在你有课的时候才有效。

/*Directories that contain classes*/
$classesDir = array (
    ROOT_DIR.'classes/',
    ROOT_DIR.'firephp/',
    ROOT_DIR.'includes/'
);
function __autoload($class_name) {
    global $classesDir;
    foreach ($classesDir as $directory) {
        if (file_exists($directory . $class_name . '.php')) {
            require_once ($directory . $class_name . '.php');
            return;
        }
    }
}

如果你想包含一堆类，而不必一次定义每个类，你可以使用:

$directories = array(
            'system/',
            'system/db/',
            'system/common/'
);
foreach ($directories as $directory) {
    foreach(glob($directory . "*.php") as $class) {
        include_once $class;
    }
}

这样你就可以在包含这个类的php文件中定义这个类，而不是整个$thisclass = new thisclass();

至于它处理所有文件的效果如何?我不确定这可能会有轻微的速度下降。

foreach (glob("classes/*.php") as $filename)
{
    include $filename;
}

2017年如何做到这一点:

spl_autoload_register( function ($class_name) {
    $CLASSES_DIR = __DIR__ . DIRECTORY_SEPARATOR . 'classes' . DIRECTORY_SEPARATOR;  // or whatever your directory is
    $file = $CLASSES_DIR . $class_name . '.php';
    if( file_exists( $file ) ) include $file;  // only include if file exists, otherwise we might enter some conflicts with other pieces of code which are also using the spl_autoload_register function
} );

这里由PHP文档推荐:自动加载类

你可以使用set_include_path:

set_include_path('classes/');

http://php.net/manual/en/function.set-include-path.php