How to get html label text in PHP session or in variable ?

Question

hello, i designed an html page, in that i have a lable. 

<label id="lblrs"  class="mt-3">Rs.50</label>

from lable the text which is "Rs.50" ,i want to store it in Php variable or in session.

In php i tried this below code

$getrs='<script>var price = document.getElementById("lblrs").textContent;</script>';

and this one also

$getrs='<script>var price = document.getElementById("lblrs").value;</script>';

 But i didn't get text of lable.

so help me how can i do this ?