在 WordPress 后台添加自定义字段筛选文章功能

// 按自定义字段筛选文章
add_filter( \'parse_query\', \'zm_posts_filter\' );
add_action( \'restrict_manage_posts\', \'zm_filter_field\' );

function zm_posts_filter( $query ) {
	global $pagenow;
	if ( is_admin() && $pagenow==\'edit.php\' && isset( $_GET[\'ZMINGCX_FILTER_FIELD\']) && $_GET[\'ZMINGCX_FILTER_FIELD\'] != \'\' ) {
		$query->query_vars[\'meta_key\'] = $_GET[\'ZMINGCX_FILTER_FIELD\'];
	if ( isset($_GET[\'ZMINGCX_FIELD_VALUE\'] ) && $_GET[\'ZMINGCX_FIELD_VALUE\'] != \'\' )
		$query->query_vars[\'meta_value\'] = $_GET[\'ZMINGCX_FIELD_VALUE\'];
	}
}

function zm_filter_field() {
	global $wpdb;
	$sql = \'SELECT DISTINCT meta_key FROM \'.$wpdb->postmeta.\' ORDER BY 1\';
	$fields = $wpdb->get_results( $sql, ARRAY_N );
?>
<select name=\"ZMINGCX_FILTER_FIELD\">
<option value=\"\"><?php _e( \'自定义字段\', \'zm\' ); ?></option>
<?php
	$current = isset( $_GET[\'ZMINGCX_FILTER_FIELD\'] )? $_GET[\'ZMINGCX_FILTER_FIELD\']:\'\';
	$current_v = isset( $_GET[\'ZMINGCX_FIELD_VALUE\'] )? $_GET[\'ZMINGCX_FIELD_VALUE\']:\'\';
	foreach ( $fields as $field ) {
		if ( substr($field[0],0,1) != \"_\" ){
		printf
			(
				\'<option value=\"%s\"%s>%s</option>\',
				$field[0],
				$field[0] == $current? \' selected=\"selected\"\':\'\',
				$field[0]
			);
		}
	}
?>
</select> <?php _e( \'值\', \'zm\' ); ?> <input type=\"TEXT\" name=\"ZMINGCX_FIELD_VALUE\" value=\"<?php echo $current_v; ?>\" />
<?php
}