$_GET is used to get the value of the HTML get method in PHP .
$_GET is the array of the query string in PHP.
suppose we surf URL :
https://www.ecom.com/product-detail.php?id=3052&action=show
after the question mark(?), all in the URL is the query string which we can get at PHP side by $_GET
echo $_GET['id'];
echo $_GET['action'];
it will print 305 and show for above url
by HTML form element , sending get method request as below
<form method="get" action="product-detail.php">
<input type="hidden" name="id" value="305"/>
<input type="hidden" name="action" value="show"/>
</form>
here method="get" means HTML form element method gets and on submit , it send get query string to PHP .
and we can get query string as we did previously by $_GET
echo $_GET['id'];
echo $_GET['action'];
If you don't provide any method to get or post to HTML form element, then it takes the default method as get