Combine random letters and numbers - php

Question

Does any of you know how to add random letters aswel as random numbers.
thanks for you help.
<?php
session_start();
$image = imagecreate(, );
$bgcolor = imagecolorallocate($image, , ,);
$textcolor = imagecolorallocate($image, , , );
$code = rand(00, 99);
$_SESSION['code'] = ($code);
imagestring($image, , , , $code, $textcolor);
header ("Content-type: image/png");
imagepng($image);
?>

Answer 1

I always like to do this for random letters and numbers using md5. its not completely random, but it still returns a random string with both numbers and letters.
$i = rand(100000000, 9999999999)
$i = md5($i); //creates a hashed string with 32 characters
$i = str_split($i, 10); //10 is the amount of characters of your string max 32
$i = $i[0];

Answer 2

i have a function for it
function createRandomString() {
$chars = "abcdefghijkmnopqrstuvwxyz023456789";
srand((double)microtime()*1000000);
$i = 0;
$randomstring = '' ;
while ($i <= 7) {
$num = rand() % 33;
$tmp = substr($chars, $num, 1);
$randomstring = $randomstring . $tmp;
$i++;
}
return $randomstring;
}
echo createRandomString();

Answer 3

You could do something like this.
<?php
$code = substr(md5(microtime()),rand(0,26),10);
$im = imagecreate(100, 30);
$bg = imagecolorallocate($im, 255, 255, 255);
$textcolor = imagecolorallocate($im, 0, 0, 0);
imagestring($im, 5, 0, 0, $code, $textcolor);
header('Content-type: image/png');
imagepng($im);
imagedestroy($im);
?>
Sources used:
https://stackoverflow.com/a/5438778/1978142
http://www.php.net//manual/en/function.imagestring.php