我想应用条件，它只显示在页面上，但不起作用，怎么了？

    function luc_add_cutom_fields_to_content( $content ) {

    $custom_fields = get_post_custom();

    $content .= "<div class=\'cta-div\'>";

    if( isset( $custom_fields[\'luc_name\'] ) ) {
         $content .= \'<h3> \'. $custom_fields[\'luc_name\'][0] . \'</h3>\';
    }
    if( isset( $custom_fields[\'luc_description\'] ) ) {
         $content .= \'<p> \' . $custom_fields[\'luc_description\'][0] . \'</p>\';
    }
    if( isset( $custom_fields[\'luc_action\'] ) ) {
         $content .= \'<a href=" \' . $custom_fields[\'luc_link\'][0] . \' ">\' . $custom_fields[\'luc_action\'][0] . \'</a>\';
    }
    $content .= \'</div>\';

    return $content;
} 

if( is_page() ) {
add_filter( \'the_content\', \'luc_add_cutom_fields_to_content\' );
}