[RESOLVED] Question about imagecreate

[Kal-El]

This is my code:

$text_array = array("Joel", "Almeida", "García", "Joel Almeida García");
$text = $text_array[rand(0, count($text_array)-1)];

$im = imagecreate(50, 22);
$bgColor = imagecolorallocate($im, 255, 255, 255);
$fgColor = imagecolorallocate($im,   0,   0, 0);
imagecolortransparent($im, $bgColor);
imagestring($im, 2, 0, 0, $text, $fgColor);
header('Content-Type: image/png');
imagepng($im);
imagedestroy($im); 

The above code, creates a png image from a random text....my question is: How can I calculate, by code, the corrrect values width and height of imagecreate, based on the returned text?

Thanks