This tutorial shows you how to create a simple anti-spam CAPTCHA verification code in PHP (CAPTCHA stands for: Completely Automated Public Turing test to tell Computers and Humans Apart).
Two functions for CAPTCHA: the sum of two numbers, and the lowest numbers.
The ideea is simple: before to generate the HTML code with the CAPTCHA question, and the input field for answer, we create the captcha code and save the correct answer into a $_SESSION. Then, when we want to check the captcha, we check if that session exists, and if it is the same with the answer added by the user.
// creates a SESSION with the sum of two numbers. Receives the session name
// returns an array with the two numbers
// From: // https://coursesweb.net/php-mysql/
function setCaptcha($ses_name) {
$nrs = array(mt_rand(1, 50), rand(1, 50)); // array with 2 random numbers, between 1 and 50
// if session exists, delete it, sets session with the sum of $nrs[0] and $nrs[1]
if(isset($_SESSION[$ses_name])) { unset($_SESSION[$ses_name]); }
$_SESSION[$ses_name] = $nrs[0] + $nrs[1];
return $nrs; // returns the array with the numbers
}
• In the PHP script that uses $_SESSION you must have session_start() at the beginning of the php file.
<?php
if(!isset($_SESSION)) session_start();
// creates a SESSION with the sum of two numbers. Receives the session name
// returns an array with the two numbers
// From: // https://coursesweb.net/php-mysql/
function setCaptcha($ses_name) {
$nrs = array(mt_rand(1, 50), rand(1, 50)); // array with 2 random numbers, between 1 and 50
// if session exists, delete it, sets session with the sum of $nrs[0] and $nrs[1]
if(isset($_SESSION[$ses_name])) { unset($_SESSION[$ses_name]); }
$_SESSION[$ses_name] = $nrs[0] + $nrs[1];
return $nrs; // returns the array with the numbers
}
// call the function to set the captcha answer in $_SESSION['captcha'], and gets the numbers
$nrs = setCaptcha('captcha');
// sets the captcha question
$ver_question = $nrs[0] .' + '. $nrs[1];
?>
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8" />
<title>Captcha anti-spam verification PHP Tutorial - https://CoursesWeb.net/</title>
<meta name="description" content="PHP Tutorial, how to create simple a Captcha anti-spam verification, from https://CoursesWeb.net/" />
<meta name="keywords" content="php tutorial, captcha, coursesweb.net" />
</head>
<body>
<form action="some_file.php" method="post">
Name: <input type="text" name="yname" /><br/>
What is the sum of: <span style="font-weight:800; font-size:1.1em; color:#0001e8;">
<?php echo $ver_question; ?>
</span> <input type="text" name="vcptca" size="3" /><br/>
<input type="submit" name="fsbmt" value="send" />
</form>
</body>
</html>
<?php
if(!isset($_SESSION)) session_start();
// if form with $_POST['vcptca'] is submited and $_SESSION['captcha'] exists
if(isset($_POST['vcptca']) && isset($_SESSION['captcha'])) {
// if the value added in 'vcptca' is equal with the value stored in session outputs Correct
// otherwise, outputs Incorrect
if($_POST['vcptca'] == $_SESSION['captcha']) {
echo 'Correct '. $_SESSION['captcha'];
}
else {
echo 'Incorrect answer.';
}
}
else {
echo 'No form submited';
}
// creates a SESSION with the lowest number between four numbers. Receives the session name
// returns an array with the four numbers
// From: // https://coursesweb.net/php-mysql/
function setCaptcha2($ses_name) {
// creates an array with values from 1 to 100
$nrs = range(1, 100);
// randomizes the order of the elements in $nrs, extracts and keeps the first 4 items
shuffle($nrs);
$nrs = array_slice($nrs, 0, 4);
// if session exists, delete it, sets session with the lowest number
if(isset($_SESSION[$ses_name])) { unset($_SESSION[$ses_name]); }
$_SESSION[$ses_name] = min($nrs);
return $nrs; // returns the array with the numbers
}
- Then, just calls this function, setCaptcha2(), to get the array with 4 numbers (the lowest number will be stored in $_SESSION), and use implode() to get a string with the numbers, to add it in the verification question.
<?php
// Here add the setCaptcha2() function
// sets the captcha answer in $_SESSION['captcha'], and gets the numbers
$nrs = setCaptcha2('captcha');
// sets the string with the numbers for verification question
$ver_question = 'Add the lowest number ('. implode(', ', $nrs) .')';
echo $ver_question; // displays the string
<p>Address: <strong>http://CoursesWeb.net/</strong> - Tutorials.</p>
#id {
font-weight: 800;
}function someFunction() { alert("CoursesWeb.net"); }
setInterval("someFunction()", 2000);$vname = 8; echo $vname;