How can PHP functions be used to prevent unwanted links from being entered in a forum?

Unwanted links can be prevented from being entered in a forum by creating a PHP function that checks user input for any URLs and rejects them if found. This can be achieved by using regular expressions to search for common URL patterns and then validating the input against these patterns before allowing it to be posted on the forum. 

function preventUnwantedLinks($input) {
    $pattern = '/(http|https):\/\/[a-zA-Z0-9\-.]+\.[a-zA-Z]{2,}(\/\S*)?/';
    
    if(preg_match($pattern, $input)) {
        return false; // reject input if URL is found
    } else {
        return true; // allow input if no URL is found
    }
}

// Example usage
$userInput = $_POST['user_input'];
if(preventUnwantedLinks($userInput)) {
    // Input is safe to be posted on the forum
} else {
    // Reject input with unwanted links
}

Keywords

PHP functions link validation regular expressions string manipulation forum security

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