function strip_param_from_url( $url, $param ) {
    $base_url = strtok($url, '?');              // Get the base url
    $parsed_url = parse_url($url);              // Parse it 
    $query = $parsed_url['query'];              // Get the query string
    parse_str( $query, $parameters );           // Convert Parameters into array
    unset( $parameters[$param] );               // Delete the one you want
    $new_query = http_build_query($parameters); // Rebuilt query string
    return $base_url.'?'.$new_query;            // Finally url is ready
}
// Usage
echo strip_param_from_url( 'http://url.com/search/?location=london&page_number=1', 
    'location' )