Clarification of search function

[Anon]

Well as most of us are I am new to php and am a little over my head and have created a search function that finds ("select * from portfolios,students where students.id=portfolios.id") I understand this part and I understand the $mode. What I do not understand is what: like '%" . implode("%' $Mode title like '%",$words) . " %'",$db); is doing? What does "%' stand for?

$Domain = 1;
if ($SearchType=="Keyword") {
$words = split(" ", $keywords);
if ($Mode=="") {$Mode="OR";}
if ($Domain=="title") {

	$result = mysql_query("select * from portfolios,students where students.id=portfolios.id like '%" . implode("%' $Mode title like '%",$words) . " %'",$db);

	} else {

		$result = mysql_query("select * from portfolios,students where students.id=portfolios.id like '%" . implode(" %' $Mode description like '%",$words) . " %' OR title like '%" . implode(" %' $Mode title like '%",$words) . " %'",$db);

[Anon]

I'm creating an adding form. My form doesn't work better I must fill in every date field then my form can be inserted correctly. But some of the date field maybe empty. How can I control that in my php script so I can insert those empty date fields.

I tried like:
if(date=='')
date=null;
it doesn't work. Thanks!!!!!!