Question

This is returning undefined, even though var roommate contains the correct value:

JS

roommate = $("#roommate").val();

$.post('roommateSearch.php', 'val=' + $(roommate).val(), function (response) {
    alert(response);
});

roommateSearch.php

<?php
$roommate = $_POST['val'];
echo "I got your value!".$roommate;
?>

Answer 1

var roommate = $("#roommate").val(); 

$.post('roommateSearch.php', 'val=' + roommate, function (response) {
    alert(response);
});

roommates is holding a value so you can use it like this 'val=' + roommate

No fancy jquery around it.