Wordpress modify meta query

Question

I have loop in functions.php with this code:

$meta_query[] = array(
                'key'       => '$key',
                'value'     => $value,
                'compare'   => 'IN',
            );  

and i trying to add next $meta_query after loop but with "<" in compare. When I add 'IN' it's working but when i change to '>=" or ">" it doesn't work.

  $meta_query[] = array(
                'key'       => 'price',
                'value'     => $value,
                'compare'   => '>=',
            );

Do you know why?

This is my fullcode:

// array of filters (field key => field name)
    $GLOBALS['my_query_filters'] = array( 
        'field_1'   => 'type', 
        'field_2'   => 'price',
        'field_3'   => 'type2',
        'field_4'   => 'city',
        'field_5'   => 'price_min',
        'field_6'   => 'price_max',
    );
    function my_pre_get_posts( $query ) {
        global $post;
        global $wpdb;
        $parametry = get_field_objects($post->ID);
        if(!is_single() && $post->ID != 2 && $query->get( 'cat' )){
            /* start filter*/
            $meta_query = $query->get('meta_query');
            foreach( $GLOBALS['my_query_filters'] as $key => $name ) {
                // continue if not found in url
                if( empty($_GET[ $name ]) ) {
                    continue;
                }

                // get the value for this filter
                // eg: http://www.website.com/events?city=melbourne,sydney
                $value = explode(',', $_GET[ $name ]);
                // append meta query

                if($name == 'price_min'){
                    $meta_query[] = array(
                        'key'       => 'price',
                        'value'     => $value,
                        'compare'   => '>=',
                    );  
                }
                elseif($name == 'price_max'){
                    $meta_query[] = array(
                        'key'       => 'price',
                        'value'     => $value,
                        'compare'   => '<=',
                    );  
                }
                else{
                    $meta_query[] = array(
                        'key'       => $name,
                        'value'     => $value,
                        'compare'   => 'IN',
                    );  
                }


            } 
            // update meta query
            $query->set('meta_query', $meta_query); 

In URL (and in table wp_postmeta) i have: type, type2, price and city. I don't have price_min and price_max so I want operate on price field.

This is my working array after filtering:

Array ( [0] => Array ( [key] => type [value] => Array ( [0] => flat) [compare] => IN ) [1] => Array ( [key] => city[value] => Array ( [0] => Cracow) [compare] => IN ) )

and this is not working array when I add price_min and price_max:

Array ( [0] => Array ( [key] => type [value] => Array ( [0] => flat) [compare] => IN ) [1] => Array ( [key] => city [value] => Array ( [0] => Cracow) [compare] => IN ) [2] => Array ( [key] => price [value] => Array ( [0] => 50000 ) [compare] => >= ) [3] => Array ( [key] => price [value] => Array ( [0] => 300000 ) [compare] => <= ) )

Answer 1

It's likely that the $value is not an integer so trying to compare the value of it as an integer when it's a string will cause some issues. Before your WP_Query arguments, place this code in your file:

$value = (int) $value;

Take a look at type juggling in PHP for more info.

This is the documentation for WP_Query meta comparisons.