PHP Form token prevent repeat submit principle

Example, session method

code is as follows

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<?p HP if ($_post) {     if ($_session["token"]!=$_post["token"]) {          die ("illegal submission!") ");    }else{         echo "secure submission!";    } } $_session["token"]=md5 (rand (1,999));//form not generated once, modify value once, do not modify it before post processing, or you cannot compare to Www.111cn.net ?> <form action= "1.php" method= "POST" <input type= "hidden" value= "<?php echo $_session[" token "]?>" Name= "token" <input type= "Submit" value= "commit"/> </form>

Example, Cookie+md5 method

The code is as follows

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<?php $value = $_cookie["value"]; Read the cookie value that was last set if (count ($_post)) { $long = ""; while (list ($key, $value) =each ($_post)) $long. = $value; $hash = MD5 ($long); Setcookie ("Value", $hash, Time () +60*60);//Reset Cookies } if ($value!= $hash) { Further operation of the data if the MD5 value is not the same two times } else { If the value of two times MD5 is the same, inform the user that the submission failed, and submit the form for duplicate } ?>