php 正则表达式提取图片url程序

//

//要替换的内容   
    $content = '



';

    //提取图片路径的src的正则表达式
    preg_match_all("/]+>/isU",$content,$matches);

            $img = "";
            if(!empty($matches)) {
            //注意，上面的正则表达式说明src的值是放在数组的第三个中
                $img = $matches[2];
            }else {
                $img = "";
            }
            if (!empty($img)) {
                $img_url = "http://".$_SERVER['SERVER_NAME'];

                $patterns= array();
                $replacements = array();

                foreach($img as $imgItem){

                $final_imgUrl = $img_url.$imgItem;
                $replacements[] = $final_imgUrl;

                $img_new = "/".preg_replace("///i","/",$imgItem)."/";
                $patterns[] = $img_new;

                }

                //让数组按照key来排序
                ksort($patterns);
                ksort($replacements);

                //替换内容
                $vote_content = preg_replace($patterns, $replacements, $content);