How can PHP be used to prevent spam posts on a website's comment section?

Spam posts on a website's comment section can be prevented by implementing a captcha system, using honeypot fields, or filtering comments based on certain criteria such as keywords or URLs commonly found in spam. One way to do this using PHP is to create a captcha field that users must fill out before submitting a comment. 

<?php
session_start();

if ($_SERVER["REQUEST_METHOD"] == "POST") {
    if (isset($_POST['captcha']) && $_POST['captcha'] == $_SESSION['captcha']) {
        // Comment is not spam, process it
        // Your comment processing code here
    } else {
        // Captcha verification failed, treat as spam
        echo "Captcha verification failed. Please try again.";
    }
}

// Generate a random captcha code and store it in session
$captcha = substr(str_shuffle("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"), 0, 6);
$_SESSION['captcha'] = $captcha;
?>

<form method="post" action="">
    <label for="comment">Comment:</label><br>
    <textarea id="comment" name="comment"></textarea><br>
    
    <label for="captcha">Enter the code shown above:</label><br>
    <input type="text" id="captcha" name="captcha" maxlength="6"><br>
    <img src="captcha_image.php" alt="Captcha Image"><br>
    
    <input type="submit" value="Submit">
</form>

Keywords

PHP spam prevention comment section form validation captcha

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