Example Analysis of PHP Imitation QQ Verification Code

Example Analysis of PHP Imitation QQ Verification Code_PHP Tutorial

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Release： 2016-07-21 15:01:58

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Copy code The code is as follows:

/**
 * Imitation QQ verification code 
*/
 //Session save path
$sessSavePath = dirname(__FILE__)."/../data/sessions/";
if(is_writeable($sessSavePath) && is_readable($sessSavePath)){ session_save_path($sessSavePath) ; }
session_start();
//Get random characters
$rndstring = '';
for($i=0; $i<4; $i++) $rndstring .= chr( mt_rand(65,90));
$img_height=45; //First define the length and width of the image
$img_width=10;
//If GD is supported, draw
if(function_exists ("imagecreate"))
{
 //In some cases, Firefox may request multiple times. Refreshing the page within 5 seconds will not change the session
 $ntime = time();
 if( empty($_SESSION['dd_ckstr_last']) || empty($_SESSION['dd_ckstr']) || ($ntime - $_SESSION['dd_ckstr_last'] > 5))
 {
 $_SESSION[ 'dd_ckstr'] = strtolower($rndstring);
 $_SESSION['dd_ckstr_last'] = $ntime;
 }
 $rndstring = $_SESSION['dd_ckstr'];
 $rndcodelen = strlen ($rndstring);
 //Create an image and set the background color
 $im = imagecreate(46,20);
 ImageColorAllocate($im, 240,243,248);
 //Interference line
 $lineColor1 = ImageColorAllocate($im, mt_rand(174,218),mt_rand(190,225),mt_rand(217,237));
 for($j=1;$j<=2;$j=$j+3)
 {
 imageline($im,0,$j+mt_rand(1,15),48,$j+mt_rand(1,15),$lineColor1);
 }
 //Output text 
 $fontColor = ImageColorAllocate($im, mt_rand(0,150),mt_rand(0,150),mt_rand(0,150));
 for($i=0;$i<$rndcodelen;$i++)
 { 
 $bc = mt_rand(0,1);
 $rndstring[$i] = strtoupper($rndstring[$i]);
 imagestring($im,mt_rand(3,5),$i *$img_height/4+mt_rand(1,5),mt_rand(1,$img_width/2), $rndstring[$i], $fontColor);
 }
 header("Pragma:no-cache" r"n");
 header("Cache-Control:no-cache"r"n");
 header("Expires:0"r"n");
 //Output specific type The image format, the priority is gif -> jpg ->png
 if(function_exists("imagepng"))
 {
 header("content-type:image/png"r"n" );
 imagepng($im);
 }
 else
 {
 header("content-type:image/jpeg"r"n");
 imagejpeg($im );
 }
 ImageDestroy($im);
 exit();
}
else
{
 //GD is not supported, only the letters ABCD are output
 $_SESSION['dd_ckstr'] = "abcd";
 $_SESSION['dd_ckstr_last'] = ''; 
 header("content-type:image/png"r"n");
 header ("Pragma:no-cache"r"n");
 header("Cache-Control:no-cache"r"n");
 header("Expires:0"r"n"); 
 $fp = fopen("data/vdcode.jpg","r");
 echo fread($fp,filesize("data/vdcode.jpg"));
 fclose($fp) ;
 exit();
}
?>