/**
* @desc：正则匹配类
* @author [Lee] <[<complet@163.com>]>
* @method
* 1、geturl         获取所有超链接
* 2、getimg         获取所有图片
* 3、getaudio           获取所有音频文件
* 4、getvideo           获取所有视频文件
* 5、getparagraph       获取所有段落
* 6、getuser            获取自定义内容         preg 自定义正则，如：/<h2>(.*)<h2>/Ui
*/
class match{
private $content = '';
/*
 @desc：构造方法，初始化待匹配文本
 */
public function __construct($content){
    $this->content = $content;
}
/*
 @desc：获取所有超链接
 @return：所有匹配的超链接
 */
public function geturl(){
    $content = $this->content;
    $preg = '/<[a|A].*?href=[\'\"]{0,1}([^>\'\"\ ]*).*?>/i';
    $bool = preg_match_all($preg,$content,$res);
    $urls = array();
    if($bool){
        $urls = $res[1];
    }
    return array_unique($urls);
}
/*
 @desc：获取所有图片
 @return：所有匹配的图片
 */
public function getimg(){
    $content = $this->content;
    $preg="/(src)=(\\\?)([\"|']?)([^ \"'>]+\.(gif|jpg|jpeg|bmp|png|svg))\\2\\3/i";
    $bool = preg_match_all($preg,$content,$res);
    $imgs = array();
    if($bool){
        $imgs = $res[4];
    }
    return array_unique($imgs);
}
/*
 @desc：获取所有音频文件
 @return：所有匹配的音频文件
 */
public function getaudio(){
    $content = $this->content;
    $preg="/(src)=(\\\?)([\"|']?)([^ \"'>]+\.(mp3|wav|wma|ogg|ape|acc))\\2\\3/i";
    $bool = preg_match_all($preg,$content,$res);
    $audios = array();
    if($bool){
        $audios = $res[4];
    }
    return array_unique($audios);
}
/*
 @desc：获取所有视频文件
 @return：所有匹配的视频文件
 */
public function getvideo(){
    $content = $this->content;
    $preg="/(src)=(\\\?)([\"|']?)([^ \"'>]+\.(swf|flv|mp4|rmvb|avi|mpeg|ra|ram|mov|wmv)((\?[^ \"'>]+)?))\\2\\3/i";
    $bool = preg_match_all($preg,$content,$res);
    $videos = array();
    if($bool){
        $videos = $res[4];
    }
    return array_unique($videos);
}
/*
 @desc：获取所有段落文本
 @return：所有匹配的段落文本
 */
public function getparagraph(){
    $content = $this->content;
    $preg="/<p>(.*)<\/p>/Ui";
    $bool = preg_match_all($preg,$content,$res);
    $paragraphs = array();
    if($bool){
        $paragraphs = $res[1];
    }
    return array_unique($paragraphs);
}
/*
 @desc：获取所有自定义内容
 @return：所有匹配的自定义内容
 */
public function getuser($preg){
    $content = $this->content;
    $bool = preg_match_all($preg,$content,$res);
    $users = array();
    if($bool){
        $users = $res[1];
    }
    return array_unique($users);
}
}

$match = new match($str);
$ret = $match->getimg();
var_dump($ret);

array(7) {
[0]=>
string(61) "https://assets-cdn.github.com/images/search-shortcut-hint.svg"
[1]=>
string(69) "https://assets-cdn.github.com/images/spinners/octocat-spinner-128.gif"
[2]=>
string(75) "https://assets-cdn.github.com/images/spinners/octocat-spinner-32-EAF2F5.gif"
[3]=>
string(68) "https://assets-cdn.github.com/images/spinners/octocat-spinner-32.gif"
[14]=>
string(45) "https://badges.gitter.im/walkor/Workerman.svg"
[15]=>
string(48) "https://cache.tdyun.com/upload/information/20200310/52/106945.jpg"
[16]=>
string(42) "http://donate.workerman.net/img/donate.png"
}