Description
Retrieves a modified URL query string.You can rebuild the URL and append query variables to the URL query by using this function.
There are two ways to use this function; either a single key and value, or an associative array.
Using a single key and value:
add_query_arg( 'key', 'value', 'http://example.com' );
Using an associative array:
add_query_arg( array(
'key1' => 'value1',
'key2' => 'value2',
), 'http://example.com' );
Omitting the URL from either use results in the current URL being used
(the value of `$_SERVER['REQUEST_URI']`).
Values are expected to be encoded appropriately with urlencode() or rawurlencode().
Setting any query variable's value to boolean false removes the key (see remove_query_arg()).
Important: The return value of add_query_arg() is not escaped by default. Output should be
late-escaped with esc_url() or similar to help prevent vulnerability to cross-site scripting
(XSS) attacks.