Look at this code:
<form method="post" action="send.php">
Phone: <input type="tel" pattern="[0-9]{3}-[0-9]{2}-[0-9]{3}">
<input type="submit" value="Validate">
</form>
Look at this code:
<form method="post" action="send.php">
Phone: <input type="tel" pattern="[0-9]{3}-[0-9]{2}-[0-9]{3}">
<input type="submit" value="Validate">
</form>