常用正则表达式

获取图片标签src 

$a = '<p>这是第一行，<br/></p><p><img src="/we/addons/wx_crec/images/20190313/1552442698518458.jpg" title="1552442698518458.jpg" alt="foot_tu.jpg" width="495" height="274"/></p><p>这里是第二行文字 </p>';
preg_match_all('/src=[\'\"]?([^\'\"]*)[\'\"]?/i', $a, $match);

var_dump($match);

//结果为
array (size=2)
  0 => 
    array (size=1)
      0 => 'src="/we/addons/wx_crec/images/20190313/1552442698518458.jpg"' 
  1 => 
    array (size=1)
      0 => string '/we/addons/wx_crec/images/20190313/1552442698518458.jpg' (length=55)

　2.指定的HTML标签批量替换

preg_match_all ("/<mpvoice(.*)<\/mpvoice>/U",$a,$pat_array);   //$a为准备要处理的内容string  从<mpvoice开始到/mpvoice>结束
$f = '';
if(!empty($pat_array[0])){
    foreach ($pat_array[0] as $key => $value) {
        //var_dump($value);
        $f.= str_replace($value, 'AAA', $a);
    }
   print_r($f);
}

 3.验证是否带有http或https的:   

if(!preg_match('/(http|https):\/\/([\w.]+\/?)\S*/', $result->video_url)){}

if(preg_match("/^(http:\/\/|https:\/\/).*$/",$a)){}