PHP 封装函数获取图片绝对路径 [ 新手入门 ]

<?php
/**
 * 获取图片绝对路径
 */
public static function listDir($dir = null)
{
    $pngList = array();
    if (! file_exists($dir)) {
        return $pngList;
    }
    if (is_dir($dir)) {
        $dir_handle = opendir($dir);
        if ($dir_handle) {
            while (false !== ($file_name = readdir($dir_handle))) {
                $key = basename($file_name);
                $keyArr = explode(".", $key);
                if (isset($keyArr[1]) && $keyArr[0] !== '') {
                    $pngList[$key] = $dir . "/" . $file_name;
                }
            }
        }
    } else {
        return $pngList;
    }
    ksort($pngList);
    return $pngList;
}