need complex search query HELP!!

[Space_Cowboy]

Hi guys, im strugling with building a complex search query.

I have a table database with 8 fields in one table. None of the fields are complsary.
On the search form the user can fill in any/all of the 8 fields to build their search.
My problem is that for any field that the user does not input a search keyword into, instead of the search query realisin that the user does not know data for that field it presumes there is no data for the blank fields.

Basically I need a search query that works like the following below (the below does not work and I realise it shouldnt, but you will see how I need it to work:

<?php
$GetContact = "SELECT * FROM contacts LEFT JOIN schools ON con_sch_id = sch_id WHERE con_client_id = '$client' AND 
if ($keyword1) {
con_firstname LIKE '%".$keyword1."%' AND
}
if ($keyword2) {
con_lastname LIKE '%".$keyword2."%' AND
}
if ($keyword3) {
con_school LIKE '%".$keyword3."%' AND
}
if ($keyword4) {
con_age LIKE '%".$keyword4."%' AND
}
if ($keyword5) {
con_form LIKE '%".$keyword5."%' AND
}
if ($keyword6) {
con_loe LIKE '%".$keyword6."%' AND
}
if ($keyword7) {
con_town LIKE '%".$keyword7."%' AND
}
if ($keyword8) {
con_city LIKE '%".$keyword8."%' 
}
ORDER BY con_lastname asc, con_firstname asc";
$ResultContact = mysql_query($GetContact);
$TableRows = mysql_num_rows($ResultContact);
?>

[php-pendejo]

<form method="POST" action="INDEX.PHP">
<p>SEARCH 1<input type="text" name="KW1" size="20"></p>
<p>SEARCH 2<input type="text" name="KW2" size="20"></p>
<p>SEARCH 3<input type="text" name="KW3" size="20"></p>
<p>SEARCH 4<input type="text" name="KW4" size="20"></p>
<p>SEARCH 5<input type="text" name="KW5" size="20"></p>
<p>SEARCH 6<input type="text" name="KW6" size="20"></p>
<p>SEARCH 7<input type="text" name="KW7" size="20"></p>
<p>SEARCH 8<input type="text" name="KW8" size="20"></p>
<p><input type="submit" value="Submit" name="B1"></p>
</form>

<?php
$keyword1 = $POST['KW1'];
$keyword2 = $POST['KW2'];
$keyword3 = $POST['KW3'];
$keyword4 = $POST['KW4'];
$keyword5 = $POST['KW5'];
$keyword6 = $POST['KW6'];
$keyword7 = $POST['KW7'];
$keyword8 = $POST['KW8'];

$GetContact = "SELECT * FROM contacts LEFT JOIN schools ON con_sch_id = sch_id WHERE con_client_id = '$client' AND";
if ($keyword1 != "") {
$GetContact .= "con_firstname LIKE '&#37;".$keyword1."%' AND";
}
if ($keyword2 != "") {
$GetContact .= "con_lastname LIKE '%".$keyword2."%' AND";
}
if ($keyword3 != "") {
$GetContact .= "con_school LIKE '%".$keyword3."%' AND";
}
if ($keyword4 != "") {
$GetContact .= "con_age LIKE '%".$keyword4."%' AND";
}
if ($keyword5 != "") {
$GetContact .= "con_form LIKE '%".$keyword5."%' AND";
}
if ($keyword6 != "") {
$GetContact .= "con_loe LIKE '%".$keyword6."%' AND";
}
if ($keyword7 != "") {
$GetContact .= "con_town LIKE '%".$keyword7."%' AND";
}
if ($keyword8 != "") {
$GetContact .= "con_city LIKE '%".$keyword8."%'";
}
$GetContact .= "ORDER BY con_lastname asc, con_firstname asc";
$ResultContact = mysql_query($GetContact);
$TableRows = mysql_num_rows($ResultContact);
?>

[Space_Cowboy]

Thanks but that doesnt work, it brings up this message:

Warning: mysql_num_rows(): supplied argument is not a valid MySQL result