I'm trying to add custom fields to my search so that it can be refined by meta values. Currently I have added some select lists to my normal search:

<form role="search" action="<?php echo site_url('/'); ?>" method="get" id="searchform">
    <input type="hidden" name="s" value="carcpt" /> <!-- // hidden 'products' value -->

    <select name="price">
        <option value="">Nothing</option>
        <option value="500.00">500.00</option>
        <option value="100.00">100.00</option>
        <option value="50.00">50.00</option>

    <select name="year">
        <option value="">Nothing</option>
        <option value="2011">2011</option>
        <option value="2007">2007</option>
        <option value="1991">1991</option>

    <input type="submit" alt="Search" value="Search" />

and at the top of my search.php I have this conditional:

$q = get_search_query();
if($q = 'carcpt'){

    $price = $_GET['price'];
    $year = $_GET['year'];

    $search = new WP_Query(
            'post_type' => 'carcpt',
            'meta_query' => array(
                    'key' => '_price',
                    'value' => $price
                    'key' => '_year',
                    'value' => $year

That's the scenario - I have 2 questions:

1) This seems like a very 'hacky' way to add and refine my search results by custom fields - is there a better / more widely accepted way to do this?

2) The problem with the query above is that if the user does not enter a price or year - it will run the query and return only post with empty price/year meta. In my query is there a way to determine if a meta is empty and modify my query accordingly - not including a switch?

  • Be careful when using straight $_GET because those, if not escaped, can actually run malicious code. Ensure that you run something like: $p = (string) $_GET['price']; then use $p in your query. – Chad Nov 26 '15 at 16:31
  • @chad $_GET values are already in string format by default and some of the WordPress functions like WP_Query run through prepare() statements which make sure the string can be safely inserted or queried through the database. There's nothing that could be put into $_GET['price'] that would bring down the system or cause a vulnerability, only a query that returns no results. You can also read into PHP: PDO::prepare. – Howdy_McGee Nov 26 '15 at 16:58

1) I think that your solution is perfectly acceptable in terms of the "right way" - post meta is intended for searching. Doesn't seem hacky to me.

2) What you should do is build the meta_query separately:

$meta_query = array();

if( !empty( $_GET['price'] ) ) {
    $meta_query[] = array( 'key' => '_price', 'value' => $_GET['price'] );
if( !empty( $_GET['year'] ) ) {
    $meta_query[] = array( 'key' => '_year', 'value' => $_GET['year'] );

$search = new WP_Query( array(
    'post_type' => 'carcpt',
    'meta_query' => $meta_query
) );

This way you're only querying on meta keys that have a supplied, non-empty value.

I would like to point out that modification of query variables is better done in the pre_get_posts action, otherwise, as in this instance two queries will be executed: one for the search of 'carcpt', and then the second query for the 'carcpt' post type and meta query.

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