How can HTML and Java code be prevented from being entered into a signature field on a website?

To prevent HTML and Java code from being entered into a signature field on a website, you can use PHP to sanitize the input by stripping out any HTML or JavaScript tags before saving the data to the database. This can help prevent potential security vulnerabilities such as cross-site scripting attacks.

// Sanitize signature input to prevent HTML and Java code
$signature = strip_tags($_POST['signature']);