How to add dropdown dynamically

How to add dropdown dynamically

I am trying to add the dynamic drop down through javascript.
i have a dropdown which has numbers, when selected creates the drop down.
but i want to add the dynamic dropdown through javascript. how can i do
this?
here is php code
code:
<?php
try {
$dbh = new
PDO('mysql:dbname=theaterdb;host=localhost','tiger','tiger');
} catch (PDOException $e) {
echo 'Connection failed: ' . $e->getMessage();
}
$sql = "SELECT theater_name FROM theater;";
$sth = $dbh->prepare($sql);
$sth->execute();
echo "<select name='theater_name' id='course'
onchange='showUser(this.value);'>";
echo "<option>----Select Theater----</option>";
while($row = $sth->fetch(PDO::FETCH_ASSOC)) {
echo "<option value='" . $row['theater_name'] ."'>" .
$row['theater_name']. "</option>";
}
echo "</select>";
?>
This php code gets the drop down values from mysql database. but this drop
down will be created dynamically from javascript
javascript code
function create(param) {
'use strict';
var i, target = document.getElementById('screens');
target.innerHTML = '';
for(i = 0; i < param; i += 1) {
target.innerHTML +='</br>';
target.innerHTML +='Movie in hall '+i+' ';
target.innerHTML += '<?php
try {
$dbh = new
PDO('mysql:dbname=theaterdb;host=localhost','tiger','tiger');
} catch (PDOException $e) {
echo 'Connection failed: ' . $e->getMessage();
}
$sql = "SELECT theater_name FROM theater;";
$sth = $dbh->prepare($sql);
$sth->execute();
echo "<select name='theater_name' id='course'
onchange='showUser(this.value);'>";
echo "<option>----Select Theater----</option>";
while($row = $sth->fetch(PDO::FETCH_ASSOC)) {
echo "<option value='" . $row['theater_name'] ."'>" .
$row['theater_name']. "</option>";
}
echo "</select>";
?>';
target.innerHTML +=' '+'Timings '+' ';
target.innerHTML += '<input type="text" name="timings">';
target.innerHTML +='</br>';
target.innerHTML +='</br>';
}
}
so now i have added this php code in javascript but it is not creating the
dropdown..
Why? How can i do this