Crop from top, not from center

I have a script that crops the image from the center, is there any way to make it crop from top of the image? I tried to do it, but I just messed up the code.

Here is the script for the cropping:

if($crop){
    $new_image = imagecreatetruecolor($width, $height);

    if($current_ratio > $desired_ratio_after){
        $new_width = $old_width * $height / $old_height;
    }

    if($current_ratio > $desired_ratio_before && $current_ratio < $desired_ratio_after){
        if( $old_width > $old_height ){
            $new_height = max( $width, $height );
            $new_width = $old_width * $new_height / $old_height;
        }
        else{
            $new_height = $old_height * $width / $old_width;
        }
    }

    if($current_ratio < $desired_ratio_before){
        $new_height = $old_height * $width / $old_width;
    }

    $width_ratio = $old_width / $new_width;
    $height_ratio = $old_height / $new_height;

    $src_x = floor( ( ( $new_width - $width ) / 2 ) * $width_ratio );
    $src_y = round( ( ( $new_height - $height ) / 2 ) * $height_ratio );
}