PHP中如何在服务器上git clone下载github资源？

PHP中如何在服务器上git clone下载github资源？

网上搜了一个，通过exec命令执行

<?php
   /**
     * This function handles the pull / init / clone of a git repo
     *
     * @param $git_url Example
     *            of git clone url git://github.com/someuser/somerepo.git
     *
     * @return bool true
     */
    public static function pullOrCloneRepo($git_url, $file_path)
    {
        if (! isset($git_url)) {
            return false;
        }
        // validate contains git://github.com/

        echo $file_path;
        if (strpos($git_url, 'git') !== FALSE) {

            if (is_dir($file_path)) {
                $first_dir = getcwd();
                // change dir to the new path
                $new_dir = chdir($file_path);
                // Git init

                $git_init = shell_exec('git init');
                // Git clone
                $git_clone = shell_exec('git clone ' . $git_url);

                // Git pull
                $git_pull = shell_exec('git pull');
                // change dir back
                $change_dir_back = chdir($first_dir);
                return true;
            }
        } else {
            return false;
        }
    }