Extract text between two markers PHP Snippet

PHP function that gets a string between two key words and/or phrases.

function textbetweenarray($s1,$s2,$s){ 
        $myarray=array(); 
        $s1=strtolower($s1); 
        $s2=strtolower($s2); 
        $L1=strlen($s1); 
        $L2=strlen($s2); 
        $scheck=strtolower($s); 

        do { 
            $pos1 = strpos($scheck,$s1); 
            if($pos1!==false){ 
                $pos2 = strpos(substr($scheck,$pos1+$L1),$s2); 
                if($pos2!==false){ 
                    $myarray[]=substr($s,$pos1+$L1,$pos2); 
                    $s=substr($s,$pos1+$L1+$pos2+$L2); 
                    $scheck=strtolower($s); 
                } 
            } 
        } while (($pos1!==false)and($pos2!==false)); 

        return $myarray; 
    }     
$str = 'hello how are you doing? hello more text doing?'; 
print_r(textbetweenarray('hello','doing?',$str));