php中htmlspecialchars与htmlentiti用法

$word = substr($str,strpos($str,'&gt',5)+4,strpos($str,"&lt",10)-strpos($str,'&gt',5)-4);
function captureKeyArray($url)
{
 $content=file_get_contents($url);
 $pattern="/<as+href=.*</a>/imsU";
 $match = array();
 preg_match_all($pattern,$content,$match);
 $matchFilter =  array();
 foreach($match[0] as $key=>$val)
    {
   $str= htmlspecialchars($val);
   if(strpos($str,"img"))
   {
   }
   else
   {
       //为什么不能直接过滤掉<,要使用&lt
     $word = substr($str,strpos($str,'&gt',5)+4,strpos($str,"&lt",10)-strpos($str,'&gt',5)-4);
     if($word!="")
     {
     array_push($matchFilter,$word);
     }
   }
    }
    return $matchFilter;
}