I used the following code to create Captcha to my form. Captcha creating well. Now I want to change font-size, and Font character spaces. I don't know how to change in the following code.
<?php
session_start();
$code= substr(str_shuffle("abcdefghijklmnopqrstuvwxyz"), 0, 6);
$_SESSION["code"]=$code;
$im = imagecreatetruecolor(150, 35);
$bg = imagecolorallocate($im, 255, 255, 255);
$fg = imagecolorallocate($im, 0, 0, 0);
imagefill($im, 5, 5, $bg);
imagestring($im, 5, 8, 8, $code, $fg);
header("Cache-Control: no-cache, must-revalidate");
header('Content-type: image/png');
imagepng($im);
imagedestroy($im);
?>