Captcha

<?php
error_reporting(E_ALL ^ E_NOTICE); 
session_start();
 
            /* Pravljenje slike*/
$img = imagecreatetruecolor(120, 30);
 
                /* Boje */
$crna = imagecolorallocate($img, 0, 0, 0);
$bela = imagecolorallocate($img, 255, 255, 255);
$siva = imagecolorallocate($img, 150, 150, 150);
$crvena = imagecolorallocate($img, 255, 0, 0);
$roze = imagecolorallocate($img, 200, 0, 150);
 
            /* Generisanje reci */
function randomRec($duzina){
$karakteri = "aBcDeFgHiJkMnOpQrStUvWxYz0123456789";
srand((double)microtime()*1000000);
$str = "";
$i = 2;
while($i <= $duzina){
$broj = rand() % 44;
$tmp = substr($karakteri, $broj, 1);
$str = $str . $tmp;
$i++;
}
return $str;
}
          /* Podesavanje Boje Pozadine */			
imagefill($img, 0, 0, $bela);
 
     /* Prikazivanje slike i ispisivanje text-a na slici */
$rec= randomRec(rand(7,10));
$_SESSION['rec']=$rec;
imagettftext($img, 15, 0, 10, 20, $crna, "calibri.ttf", $rec);
imagettftext($img, 15, 0, 13, 23, $siva, "calibri.ttf", $rec);
 
header("Content-type: image/png");
imagepng($img);
imagedestroy($img);
 
if(!$_POST['proveri']){ 
echo "<form method='POST' action='captcha.php'>"; 
echo "<table border='0' cellspacing='3' cellpadding='3'>"; 
echo "<tr><td>Upisite text koji vidie na slici:</td></tr>\n"; 
echo "<tr><td align='center'><img src='image.php' id='captcha'></td></tr>\n"; 
echo "<tr><td align='right'><input type='text' name='image'>\n"; 
echo "<a href='#' onclick=\"document.getElementById('captcha').src='image.php'\"><img src='http://www.dodaj.rs/f/P/7j/2a5B7zNh/refresh.png' /></a>"; 
echo "<tr><td align='right'><input type='submit' name='proveri' value='Check'></td></tr>\n"; 
echo "</table></form>\n"; 
}
else {
$image = $_POST['image'];
if($image == $_SESSION['rec']){
                   /* Correct text */
session_destroy();
echo "<script>alert('Text koji ste uneli je tacan!')</script>";
echo "<script>location.replace('captcha.php')</script>";
}
else {
                  /* Incorrect text */
echo "<script>alert('Text koji ste uneli je netacan!')</script>";
echo "<script>location.replace('captcha.php')</script>";
}
}
?>