Calculate proportions in php

proportions.php

function propor($nwidth, $nheight, $mwidth, $mheight) {

    $percentChange = $nwidth / $mwidth;
    $newHeight = round( ( $percentChange *$mheight ) );

    if($nheight==$newHeight ) {
            return true;
    } else {
        return false;
    }
}