Infinite scrolling - php

Question

I am trying to add some "Infinite Scrolling" to my product pages. However, i can't get it working at all, so i have nothing.
The page currently works, but it just outputs all of the products. I can't get the infinite scrolling scripts i found working, as my query is not always the same.
This is the code that builds my query, using GETs:
$kategori_q = "";
if ($kategori !== "") {
if ($hkat !== "") {
$ukator = "";
$underkategorier = sqlSelect("SELECT * FROM underkategorier WHERE fk_hkategori = '$kategori'");
while ($row = sqlFetch($underkategorier)) {
$ukator .= " fk_ukategori = '".$row['underkategori_id']."' OR";
}
$kategori_q = rtrim($ukator, "OR");
$kategori_q = "WHERE ($kategori_q)";
}
else {
$kategori_q = "WHERE fk_ukategori = '$kategori'";
}
}
$query = "SELECT * FROM annoncer $kategori_q ORDER BY annonce_id DESC";
$soeg = "";
if (isset($_GET['soeg'])) {
$soeg = $_GET['soeg'];
if (substr_count($query, "WHERE") == 1) {
$soeg = " AND (overskrift LIKE '%$soeg%' OR beskrivelse LIKE '%$soeg%')";
}
else {
$soeg = " WHERE (overskrift LIKE '%$soeg%' OR beskrivelse LIKE '%$soeg%')";
}
}
$query = "SELECT * FROM annoncer $kategori_q $soeg ORDER BY annonce_id DESC";
$q = sqlSelect($query);