how i add jquery on php code example

Example 1: jquery script tag

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>

// Put this script in the head of your index.html to load jQuery
// The Google Hosted Libraries is a stable, reliable, high-speed, 
// globally available content distribution network for the most popular, 
// open-source JavaScript libraries.

// Google works directly with the key stakeholders for each library effort 
// and accepts the latest versions as they are released.

Example 2: html include jquery

<!-- Wrap inside the head tag -->
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>