图形验证码

test.html
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验 证   

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post.php
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$randval  = mt_rand();
$seccode = substr($randval,-4);
$length    =  strlen($seccode);
$_SESSION['seccode']  =  $seccode; //用SESSION保存验证码
$img=imagecreate(60,20);
$bgcolor = imagecolorallocate($img,255,255,255);
for  ($i = 0; $i
?>
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imgCheck.php
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