PHP+Session Solution to Prevent Form Repeated Submission

index.php

The current form page is_submit is set to 0

 SESSION_START(); 
$_SESSION['is_submit'] = 0;
<form id="reg" action="post.php" method="post"> 
  <p> User name: <input type="text" class="input" name="username" id="user"></p> 
  <p> Dense  &nbsp;  Code: <input type="password" class="input" name="password" id="pass"></p> 
  <p>E-mail : <input type="text" class="input" name="email" id="email"></p> 
  <p><input type="submit" name="submit" class="btn" value=" Submit registration "/></p> 
</form>

post.php

If the form is submitted, set the current 'is_submit to 1. If post. php is refreshed, the else code will be executed

SESSION_START(); 
if (isset($_POST['submit'])) { 
  if ($_SESSION['is_submit'] == '0') { 
    $_SESSION['is_submit'] = '1'; 
    echo " Code block, things to do, code ...<a onclick='history.go(-1);' href='javascript:void(0)'> Return </a>"; 
  } else { 
    echo " Please do not submit it repeatedly <a href='index.php'>PHP+SESSION Prevent forms from being submitted repeatedly </a>"; 
  } 
}

Introduction of php Implementation Method for Solving Repeated Submission of Forms

[Introduction] Repeated submission is a problem that we often encounter in our development. Besides using js to prevent repeated submission of forms, we can also use php to prevent repeated submission.

The code for Example 1 is as follows

Repeated submission is a problem that we often encounter in our development. Besides using js to prevent repeated submission of forms, we can also use php to prevent repeated submission.

Example 1

The code is as follows

<?php
 /*
 * php How to prevent repeated submission of forms in 
 */
session_start();
 if (empty($_SESSION['ip'])) {// No. 1 1 A write operation is performed to determine whether a record has been recorded IP Address to know if you want to write to the database 
  $_SESSION['ip'] = $_SERVER['REMOTE_ADDR']; // No. 1 1 Second write, paving the way for the judgment of refreshing or retreating later 
  //...........// Write to database operation 
} else {// There is already a number 1 The operation after the second write is no longer written to the database 
  echo ' Please do not refresh and go back again '; // Write 1 Some written tips or other things 
}
 ?>

Specific principle

session range variable token to prevent.

1. Turn on session:

session_start();

2. If a form is submitted

Copy the code as follows

if (isset($token))

token is included in form in the form of hidden.

Copy the code as follows

<input type="hidden" name="token" value="<?php echo $token; ?>" /> 

3. If the form is submitted repeatedly

The code is as follows

if ($_SESSION["token"] != $token) { 
  //  Do not allow duplicate submissions, process them here  
  // header("location:".$_SERVER['PHP_SELF']); 
 } else { 
  //  Normal form submission, processed here  
  // echo " Submitted ";  
} 

4. Set the token value

The code is as follows

$token = mt_rand(0,1000000);
$_SESSION['token'] = $token;

Summarize