搜索 - 空标准字段

Question

I'm trying to create the search system with mutliple criteria fields. My question is how to handle the empty criteria fields (omitted by user) when you search by EXACT word not just it's similars (LIKE).

Code:

$prva = mysql_real_escape_string($_POST["crit1"]);
$druga = mysql_real_escape_string($_POST["crit2"]);
$tretja = mysql_real_escape_string($_POST["crit3"]);
$cetrta = mysql_real_escape_string($_POST["crit4"]);

$query = mysql_query("SELECT pointID FROM bpoint WHERE
(sName LIKE '%$prva%') AND
(sAddr LIKE '%$druga%') AND
(placeID LIKE '%$tretja%') AND
(sPhone = '$cetrta')
"); 

Someone suggested this, but i dont understand exactly how it works:

WHERE
(col1=@col1 or @col1 is null) and
(col2=@col2 or @col2 is null) and
(col3=@col3 or @col3 is null) and
.
.

thanks :)

Answer 1

$query="SELECT pointID FROM bpoint WHERE ";

if(isset($_POST['condition1']))
$condition[]="name='somename'";


if(isset($_POST['condition2']))
$condition[]="address='someaddress'";

//More condition here

if(!empty($condition))
$query .= implode(' AND ',$condition);

mysql_query($query)