echo get_post_meta of all post in a category to fill up a select field

Question

I want to retrieve a specific post_meta of all posts contained in a specific category. I want to build a search form at the top of each category with a select field which would be filled up by the required post_meta of all the post contained in the category the user is currently in. Is this doable? Maybe it's possible with a loop which would look like:

For each post_meta called "City" in all posts contained in category 'X', you must put it in <option value="City's name">City's name</option>

So far, here is what I have been able to do.

<select>
<option value="" selected="selected">Please pick a city below...</option>
<option value="<?php echo get_post_meta($post->ID, 'City', true) ?>">
<?php echo get_post_meta($post->ID, 'City', true) ?>
</option>
</select>

Not much, I know. Any help, please ? Thank you in advance.

Answer 1

I sounds like your doing this wrong. You do not typically query the post meta first in a hierarchical query since it will be much slower. I don't really know how your structuring this by your question.

The logic should be -->query category--->query posts with meta value ( or tag or sub-category, don't forget these work to).

To do this you need to use WP Query http://codex.wordpress.org/Class_Reference/WP_Query

For example $query = new WP_Query( 'cat=4&meta_key=city' );

If your using a lot of meta field values you should set get_post_meta to false or leave that parameter out to return an array ( your example has it set to true).

Answer 2

Give this a try:

<?php
$args = array( 'category' => 3, 'meta_key' => 'City' );
$lastposts = get_posts( $args );
echo '<select>';
echo '<option value="" selected="selected">Please pick a city below...</option>';
foreach($lastposts as $post) : setup_postdata($post);
    $themeta = get_post_meta($post->ID,'City',true); ?>
    <option value="<?php echo $themeta; ?>"><?php echo $themeta; ?></option>
<?php endforeach;
echo '</select>';
?>

I didn't test it but it should work. It's getting all posts from a certain category along with a certain meta key.

Answer 3

Thank you very much for your answers!

I finally found what I wanted here : http://sixrevisions.com/wordpress/custom-fields-search/ Here is the code :

<form name="search" action="" method="get">
<select name="City">
 <?php
  $metakey = 'city';
  $cities = $wpdb->get_col($wpdb->prepare("SELECT DISTINCT meta_value FROM $wpdb->postmeta WHERE meta_key = %s ORDER BY meta_value ASC", $metakey) );
  if ($cities) {
    foreach ($cities as $city) {
  echo "<option value=\"" . $city . "\">" . $city . "</option>";
    }
    }
 ?>
</select>
<input type="submit" value="search" />
</form>

This is a brilliant article and it helped me a lot! I hope it'll help others too.