PHP function to build query string from array

/**
* Builds an http query string.
* @param array $query  // of key value pairs to be used in the query
* @return string       // http query string.
**/
function build_http_query( $query ){

    $query_array = array();

    foreach( $query as $key => $key_value ){

        $query_array[] = $key . '=' . urlencode( $key_value );

    }

    return implode( '&', $query_array );

}