php:get the imag's src and alt from a html

functions.php

/**
 * get src of the first img tag from string
 * @param  [type] string
 * @param  [type] boolean if true get all the images' src
 * @return [type]      first src or none
 */
function get_img_src($str, $isAll = false){
    preg_match('/\<img.*src=\"(.*?)\"/i',$str,$src);
    preg_match('/alt\s*=\"(.*?)\"/i',$str,$alt);
    if ($isAll) {
        preg_match_all('/\<img.*src=\"(.*?)\"/i',$str,$src);
        preg_match_all('/alt\s*=\"(.*?)\"/i',$str,$alt);
    }
    $result = false;
    if($src[1]) {
        $img = array(
            "url" => $src[1],
            "alt" => $alt[1]
        );
        if ($isAll) {
            $img = array_map(function($src, $alt){
                return array( 'url' => $src, 'alt' => $alt);
            }, $src[1], $alt[1]);
        }
        $result = $img;
    }
    return $result;
}