Send a javascript var to php

Question

I try to assign a string type javascript variable to a php variable and retrieve a table from database, I wrote all the code in a file.

I read date from input:

<input type="date" id="myDate" >

and by a listener I run myDate function, it produce sql1 that is a string, it should pass sql1 to $sql, I tried that users explain in other Q's but I don't get the right answer :

<script>
var dateBut = document.getElementById("myDate")
function myDate() {
    var x = document.getElementById("myDate").value;
    document.getElementById("demo3").innerHTML = x;

    // sql1 string
    var sql1 = "SELECT * FROM TSE(" + document.getElementById("demo3").innerHTML +")";
    document.getElementById("demo2").innerHTML = sql1;

    var tbl = document.getElementById("demo");
    tbl.innerHTML = "";

    var ch = document.getElementById("checkerWork");


    <?php
    // sql1 should pass to $sql;
    $sql = ?>"SELECT * FROM TSE(" + document.getElementById("demo3").innerHTML + ")"<?php
    mysqli_set_charset($conn, "utf8");
    $result = $conn->query($sql);

    ?>

    }
dateBut.addEventListener("change", myDate, false );

all of the code is in a php file. thanks