Language: PHP Highlight Mode: PHP Last Modified: March 16th, 2009
<?PHP// start the session to store the variableSESSION_START();// generate the random code$chars='abcdefghkmnprstuvwxyzABCDEFGHJKLMNPQRSTUV2345689';$length=6;$code='';FOR($i=0;$i<$length;$i++){$pos=MT_RAND(0,STRLEN($chars)-1);$code.=SUBSTR($chars,$pos,1);}// store the code to compare later$_SESSION['captcha']=$code;// set up the image// size$width=120;$height=30;// colors$r=MT_RAND(160,255);$g=MT_RAND(160,255);$b=MT_RAND(160,255);// create handle for new image$image= imagecreate($width,$height);// create color handles$background= imagecolorallocate($image,$r,$g,$b);$text= imagecolorallocate($image,$r-128,$g-128,$b-128);// fill the background
imagefill($image,0,0,$background);// add characters in random orientationFOR($i=1;$i<=$length;$i++){$counter=MT_RAND(0,1);IF($counter==0){$angle=MT_RAND(0,30);}IF($counter==1){$angle=MT_RAND(330,360);}// "arial.ttf" can be replaced by any TTF font file stored in the same directory as the script
imagettftext($image,MT_RAND(14,18),$angle,($i*18)-8,MT_RAND(20,25),$text,"arial.ttf",SUBSTR($code,($i-1),1));}// draw a line through the text
imageline($image,0,MT_RAND(5,$height-5),$width,MT_RAND(5,$height-5),$text);// blur the image$gaussian=ARRAY(ARRAY(1.0,2.0,1.0),ARRAY(2.0,4.0,2.0),ARRAY(1.0,2.0,1.0));
imageconvolution($image,$gaussian,16,0);// add a border for looks
imagerectangle($image,0,0,$width-1,$height-1,$text);// prevent cachingHEADER('Expires: Tue, 08 Oct 1991 00:00:00 GMT');HEADER('Cache-Control: no-cache, must-revalidate');// output the imageHEADER("Content-Type: image/gif");
imagegif($image);
imagedestroy($image);?>
Sample Page:
<?PHPSESSION_START();?>
<html>
<head>
<title>CATCHA Test</title>
</head>
<body>
<?PHPIF(ISSET($_POST['captcha'])){IF(STRTOLOWER($_POST['captcha'])==STRTOLOWER($_SESSION['captcha'])){ECHO'<div>Success</div>';}ELSE{ECHO'<div>Incorrect</div>';}}?>
<img src="captcha.php" alt="CAPTCHA" width="120" height="30">
<form method="post">
<input type="text" name="captcha" id="captcha">
<input type="submit" name="submit" id="submit" value="Test">
</form>
</body>
</html>
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