帮忙看下怎么会返回null
<?php<br />
function newtripos($str,$findstr,$count,$off=0){<br />
$pos=stripos($str,$findstr,$off);<br />
$count--;<br />
if($count>0 && $pos!=false){<br />
$pos=newtripos($str,$findstr,$count,$pos+1);<br />
}else{<br />
var_dump($pos);<br />
return $pos;<br />
}<br />
}<br />
$a="456123456455654466";<br />
$b=newtripos($a,'6',4);<br />
var_dump($b);<br />
?> 
