これはバグですか?何をするか

<br />function my_bcmod( $x, $y ) {<br />    $take = 5;<br />    $mod = '';<br />    do{<br />        $a = (int)$mod.substr( $x, 0, $take );<br />        $x = substr( $x, $take );<br />        $mod = $a % $y;<br />		echo $a.'-'.$x.'-'.$mod.'<br>';<br />    }<br />    while ( strlen($x) ); <br />    return (int)$mod; <br />}<br /><br />echo my_bcmod( "7044060001970316212900", 150 );//50<br /><br />/*<br />070440-60001970316212900-90<br />9060001-970316212900-1<br />197031-6212900-81<br />8162129-00-29<br />2900--50<br />*/