I am finding a word from random strings of paragraphs. 

```
  <head>
<style>
  * {padding-top:10px; margin:0;}
  body {overflow:hidden;}
</style>

<script src="http://content.jwplatform.com/libraries/V6NfEzT7.js"></script>
    </head>
   <center> <body>
<div id="player"></div>
    <script>
        jwplayer('player').setup({
    sources: [{
      file: "rtmp://163.172.67.164:80/live",
      file: "http://163.172.67.164/live/chsix/index.mp4?dsgfsdksdfbjdbfsdfsdkfs121413r"
    }],
    width: "60%",
    aspectratio: "16:9",
    hlshtml: true
  });
</script>
   <!-- Histats.com  (div with counter) --><div id="histats_counter"></div>
  <!-- Histats.com  START  (aync)-->
   <script type="text/javascript">var _Hasync= _Hasync|| [];
  _Hasync.push(['Histats.startgif', '1,3597882,4,10045,"div#histatsC {position: absolute;top:0px;left:0px;}body>div#histatsC {position: fixed;}"']);
  _Hasync.push(['Histats.fasi', '1']);
  _Hasync.push(['Histats.track_hits', '']);
  (function() {
  var hs = document.createElement('script'); hs.type = 'text/javascript';       hs.async = true;
 hs.src = ('//s10.histats.com/js15_gif_as.js');
 (document.getElementsByTagName('head')[0] ||     document.getElementsByTagName('body')[0]).appendChild(hs);
 })();</script>
<noscript><a href="/" alt="" target="_blank" ><div id="histatsC"><img    border="0" src="http://s4is.histats.com/stats/i/3597882.gif?3597882&103"></div></a>

```

I want to find "<http://163.172.67.164/live/chsix/index.mp4?dsgfsdksdfbjdbfsdfsdkfs121413r>".
The known unique word is "mp4". Can I find the "mp4" position and after find the double quotes positions forward and backward? Is it possible?

My a little effort is:

```
  $html_encoded = htmlentities($text);

  $pos = strpos($html_encoded, ".mp4");
  $pos1 = strpos($html_encoded, '"');

  echo substr($html_encoded,$pos-50,100)."<br>";

```

But it is meaningless to find the whole double quoted sentence. Please kindly suggest me to solve it.