<?php
session_start();
$pool = '0123456789';
$img_width = 80;
$img_height = 30;
$str = '';
for ($i = 0; $i < 4; $i++){
$str .= substr($pool, mt_rand(0, strlen($pool) -1), 1);
}
$string = $str;
$im = imagecreate($img_width, $img_height);
$bg_color = imagecolorallocate($im,103,103,103);
$font_color = imagecolorallocate($im,252,252,252);
$grid_color = imagecolorallocate($im,31,0,0);
$border_color = imagecolorallocate ($im, 174, 174, 174);
imagefill($im,1,1,$bg_color);
for($i=0; $i<500; $i++){
$rand1 = rand(0,$img_width);
$rand2 = rand(0,$img_height);
imageline($im, $rand1, $rand2, $rand1, $rand2, $grid_color);
}
$x = rand(5, $img_width/(7/2));
imagerectangle($im, 0, 0, $img_width-1, $img_height-1, $border_color);
for($a=0; $a < 4; $a++){
imagestring($im, 5, $x, rand(6 , $img_height/5), substr($string, $a, 1), $font_color);
$x += (5*2); #odstêp
}
$_SESSION['string'] = $string;
header("Content-type: image/gif");
imagegif($im);
imagedestroy($im);
?>