How to stop URL query string from repeating? - php

Question

I'm using a URL query string to filter MySQL search results. When a user clicks on one of the links the query along with another variable is passed to the application, which then builds and executes a SQL query to the database.
The filtering works - the user can filter by genre, platform and can also sort at the same time, but the problem is that every time they click on a link it adds another variable at the end of $query.
For example if the user types in example and selects as filter, the genre action, the query looks like this:
keywords=example&genre=action
But lets say they then click on the adventure genre, the query then looks like this:
keywords=example&genre=action&genre=adventure
Is there a way to get the query to replace a variable if it isalready set?
$query = mysql_real_escape_string(htmlentities(trim($_SERVER[QUERY_STRING])));
<div id="filter_nav">
<ul id="nav_form">
<li><h3 id="h3">Genre: </h3>
<li>Fighting</li>
<li>Role-Playing</li>
<li>Action</li>
</ul>
<ul id="nav_form">
<li><h3 id="h3">Platform: </h3>
<li>PS3</li>
<li>Xbox 360</li>
<li>Gamecube</li>
</ul>
</div>
';
echo '
<ul id="sorting_form">
<li><h3 id="h3">SORT BY: </h3>
<li>Title</li>
<li>Date</li>
<li>Rating</li>
</ul>
';
function search_results($keywords){
$returned_results = array();
$where = "";
$keywords = preg_split('/[\s]+/', $keywords);
$total_keywords = count($keywords);
foreach($keywords as $key=>$keyword){
$where .= "title LIKE '%$keyword%'";
if($key != ($total_keywords - 1)){
$where .= " AND ";
}
}
if (isset($_GET['platform']) && !empty($_GET['platform'])){
$platform = mysql_real_escape_string(htmlentities(trim($_GET['platform'])));
$where .= " AND platform='$platform'";
}
if (isset($_GET['genre']) && !empty($_GET['genre'])){
$genre = mysql_real_escape_string(htmlentities(trim($_GET['genre'])));
$where .= " AND genre='$genre'";
}
if (isset($_GET['order']) && !empty($_GET['order'])){
$order = mysql_real_escape_string(htmlentities(trim($_GET['order'])));
$where .= " ORDER BY $order DESC";
}
$results ="SELECT * FROM games WHERE $where ";

Answer 1

Using your code it can be done de-constructing the query string using parse_url and rebuilding it using http_build_query for every link.
However, personally I would just go for a form with 3 select boxes where the previously selected values are pre-selected.
You could put all your selection options in one multi-dimensional array and do a double loop.
Example:
<?php
$options = array(
"genre" => array("Fighting", "Role-Playing", ...),
...
);
foreach $options as $key => $value)
{
?>
<select name="<?php echo $key; ?>">
<?php
foreach ($value as $item)
{
// echo option for item and mark it selected if necessary
}
?>
</select>
<?php
}
?>

Answer 2

Modify every <a> tag like:
Fighting
to
Fighting
I.e remove '.$query.' part.