How to prevent form submission if message contain links? - php

Question

can anyone help me? I'm trying to prevent spam in the contact form.
I would like to achieve this with PHP. I can't find any solution on the web. Thanks in advance for who can help me out.
HTML
<form name="myForm" id="myForm" method="post" action="contact-form.php">
<input type="text" name="name" value="" class="form-control mt-3" id="name" placeholder="Full Name" required>
<input type="email" name="email" value="" class="form-control mt-3" id="email" placeholder="Email" required>
<textarea class="form-control mt-3" name="message" id="message" placeholder="Type your message" rows="7" required></textarea>
<input type="text" id="Nomoboto" name="Nomoboto" value="800 800 1000" autocomplete="off" />
<input type="text" id="PostItBoto" name="PostItBoto" value="93940" autocomplete="off" />
<input type="text" id="Empty_Me" name="Empty_Me" value=""/>
<input type="text" id="Empty_You" name="Empty_You" value=""/>
<button type="submit" class="btn btn-primary float-right mt-3">Send Message</button>
</form>
PHP
<?php
$name = $_POST ['name'];
$email = $_POST ['email'];
$message = $_POST ['message'];
$Empty_Me = $_POST ['Empty_Me'];
$Empty_You = $_POST ['Empty_You'];
$email_from = 'Contact Form';
$email_subject = "New Form Submission";
$email_body = "User Name: $name.\n".
"User Email: $email.\n".
"User Message: $message.\n".
"Empty_Me: $Empty_Me.\n".
"Empty_You: $Empty_You.\n";
function email_validation($str) {
return (!preg_match(
"^[_a-z0-9-]+(\.[_a-z0-9-]+)*#[a-z0-9-]+(\.[a-z0-9-]+)*(\.[a-z]{2,3})$^", $str))
? FALSE : TRUE;
}
$to = "info#mail.com";
$headers = "From $email_from \r\n";
mail($to,$email_subject,$email_body,$headers);
header("Location: index.html");