Source

File: wp-includes/functions.php

function _http_build_query( $data, $prefix = null, $sep = null, $key = '', $urlencode = true ) {
	$ret = array();

	foreach ( (array) $data as $k => $v ) {
		if ( $urlencode ) {
			$k = urlencode( $k );
		}
		if ( is_int( $k ) && null != $prefix ) {
			$k = $prefix . $k;
		}
		if ( ! empty( $key ) ) {
			$k = $key . '%5B' . $k . '%5D';
		}
		if ( null === $v ) {
			continue;
		} elseif ( false === $v ) {
			$v = '0';
		}

		if ( is_array( $v ) || is_object( $v ) ) {
			array_push( $ret, _http_build_query( $v, '', $sep, $k, $urlencode ) );
		} elseif ( $urlencode ) {
			array_push( $ret, $k . '=' . urlencode( $v ) );
		} else {
			array_push( $ret, $k . '=' . $v );
		}
	}

	if ( null === $sep ) {
		$sep = ini_get( 'arg_separator.output' );
	}

	return implode( $sep, $ret );
}