PHP: Generate Dynamic Images from Text

<?php
Header ("Content-type: image/gif");

$textfile = "quote.txt";
$quotes = array();
if(file_exists($textfile)){
     $quotes = file($textfile);
     srand ((float) microtime() * 10000000);
     $string = '-'.$quotes[array_rand($quotes)];
     $string = substr($string,0,strlen($string)-2);
}
else{
     $string = "No 'Quote' available at this time.";
}
$font  = 2;
$width  = ImageFontWidth($font)* strlen($string);
$height = ImageFontHeight($font);
$im = ImageCreate($width,$height);

$x=imagesx($im)-$width ;
$y=imagesy($im)-$height;
$background_color = imagecolorallocate ($im, 242, 242, 242); //white background
$text_color = imagecolorallocate ($im, 0, 0,0);//black text
$trans_color = $background_color;//transparent colour
imagecolortransparent($im, $trans_color);
imagestring ($im, $font, $x, $y,  $string, $text_color);

imagegif($im);
ImageDestroy($im);
?>