Search with post_meta - php

Question

I write my own query to wordpress database and I'm stuck. I have many (5) custom fields like:
town
price
size
... etc
and in search.php I have:
$querystr = "
SELECT wposts.*
FROM $wpdb->posts wposts, $wpdb->postmeta wpostmeta
WHERE wposts.ID = wpostmeta.post_id ";
$town = addslashes($_GET['town']);
if($town!=''){
$querystr .= " AND wpostmeta.meta_key = 'town' AND wpostmeta.meta_value = '".$town."'";
}
$mo = addslashes($_GET['mo']);
if($mo!='' && preg_match("/^\d+$/", $mo)){
$querystr .= " AND wpostmeta.meta_key = 'price' AND wpostmeta.meta_value > '".$mo."'";
}
$md = addslashes($_GET['md']);
if($md!='' && preg_match("/^\d+$/", $md)){
$querystr .= " AND wpostmeta.meta_key = 'price' AND wpostmeta.meta_value < '".$md."'";
}
$querystr .= " AND wposts.post_status = 'publish' AND wposts.post_type = 'post'";
$pageposts = $wpdb->get_results($querystr, OBJECT);
but this does not work. If I use only one condition:
$querystr = "SELECT wposts.* FROM $wpdb->posts wposts, $wpdb->postmeta wpostmeta WHERE wposts.ID = wpostmeta.post_id ";
$town = addslashes($_GET['town']);
if($town!=''){
$querystr .= " AND wpostmeta.meta_key = 'town' AND wpostmeta.meta_value = '".$town."'";
}
$querystr .= " AND wposts.post_status = 'publish' AND wposts.post_type = 'post'";
$pageposts = $wpdb->get_results($querystr, OBJECT);
then it will work. What I'm doing wrong?

Answer 1

The select expression doesn't make sense as a whole because you have contradictive where conditions. It also doesn't make sense in relation to how relational databases work. You want to match two unique rows that share the same column names in one query, this is not possible without using techniques like subqueries.
Consider that all expression parts must be true and you got something like this:
SELECT wposts.*
FROM wp_posts wposts, wp_postmeta wpostmeta
WHERE wposts.ID = wpostmeta.post_id
AND wpostmeta.meta_key = 'town' AND wpostmeta.meta_value = 'My town'
AND wpostmeta.meta_key = 'price' AND wpostmeta.meta_value > 500
Here you say meta_key equals "town" AND meta_value equals "My town". That makes sense, but when you also say meta_key also equals "price" AND meta_value is also greater than 500. The expression will never be true and regardless the parser also has no way of grouping together the two different condition sets.
WP_Query
If possible I suggest that you use the WP_Query class instead of directly querying the database. This wrapper greatly simplifies your code and makes it easier to maintain. Note that the code requires WordPress >=3.1 as it uses the meta_query option.
Your query can be written like this:
<?php
// The arguments that defines the query
$args = array(
'post_status' => 'publish',
'post_type' => 'post'
);
// We define the meta/custom field conditions
$meta_query = array();
// PS: No need to slash the values, WordPress will do that for us
$town = $_GET['town'];
$mo = (int) $_GET['mo']; // Simple sanitizment, implement your own as see fit
$md = (int) $_GET['md']; // Simple sanitizment, implement your own as see fit
if ( $town ) {
$meta_query[] = array(
'key' => 'town',
'value' => $town
);
}
if ( $mo ) {
$meta_query[] = array(
'key' => 'price',
'value' => $mo,
'type' => 'NUMERIC',
'compare' => '>'
);
}
if ( $md ) {
$meta_query[] = array(
'key' => 'price',
'value' => $md,
'type' => 'NUMERIC',
'compare' => '<'
);
}
if ( $meta_query ) {
// Add the meta_query conditions to the arguments array
$meta_query['relation'] = 'AND';
$args['meta_query'] = $meta_query;
}
// Create WP_Query object with the arguments
$query = new WP_Query( $args );
// Fetch the posts
$posts = $query->get_posts();
// Voila!
?>