PHP CAPTCHA is used to prevent robots from entering data. It makes the form more secure.
In this example we used two file.
<?php
session_start();
if ($_POST["vercode"] != $_SESSION["vercode"] OR $_SESSION["vercode"]=='') {
echo "<script>alert('Incorrect verification code');</script>" ;
}
else{
echo "<script>alert('Verification code match !');</script>" ;
}
?>
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>Bootstrap Elegant Account Login Form with Avatar Icon</title>
<link rel="stylesheet" href="https://fonts.googleapis.com/icon?family=Material+Icons">
<link href="https://fonts.googleapis.com/css?family=Roboto|Varela+Round" rel="stylesheet">
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>
</head>
<body>
<div class="login-form">
<form action="" method="post">
<div class="avatar"><i class="material-icons"></i></div>
<h4 class="modal-title">Login to Your Account</h4>
<div class="form-group">
<input type="text" class="form-control" placeholder="Username" required="required">
</div>
<div class="form-group">
<input type="password" class="form-control" placeholder="Password" required="required">
</div>
<div class="form-group">
<input type="text" name="vercode" class="form-control" placeholder="Verfication Code" required="required">
</div>
<div class="form-group small clearfix">
<label class="checkbox-inline">Verification Code</label>
<img src="captcha.php" >
</div>
<input type="submit" class="btn btn-primary btn-block btn-lg" value="Login">
</form>
</div>
</body>
</html>
<?php
session_start();
$text = rand(10000,99999);
$_SESSION["vercode"] = $text;
$height = 25;
$width = 65;
$image_p = imagecreate($width, $height);
$black = imagecolorallocate($image_p, 0, 0, 0);
$white = imagecolorallocate($image_p, 255, 255, 255);
$font_size = 14;
imagestring($image_p, $font_size, 5, 5, $text, $white);
imagejpeg($image_p, null, 80);
?>