WP_HTTP_Proxy::send_through_proxy( string $uri )

	public function send_through_proxy( $uri ) {
		/*
		 * parse_url() only handles http, https type URLs, and will emit E_WARNING on failure.
		 * This will be displayed on sites, which is not reasonable.
		 */
		$check = @parse_url($uri);

		// Malformed URL, can not process, but this could mean ssl, so let through anyway.
		if ( $check === false )
			return true;

		$home = parse_url( get_option('siteurl') );

		/**
		 * Filters whether to preempt sending the request through the proxy server.
		 *
		 * Returning false will bypass the proxy; returning true will send
		 * the request through the proxy. Returning null bypasses the filter.
		 *
		 * @since WP-3.5.0
		 *
		 * @param null   $override Whether to override the request result. Default null.
		 * @param string $uri      URL to check.
		 * @param array  $check    Associative array result of parsing the URI.
		 * @param array  $home     Associative array result of parsing the site URL.
		 */
		$result = apply_filters( 'pre_http_send_through_proxy', null, $uri, $check, $home );
		if ( ! is_null( $result ) )
			return $result;

		if ( 'localhost' == $check['host'] || ( isset( $home['host'] ) && $home['host'] == $check['host'] ) )
			return false;

		if ( !defined('WP_PROXY_BYPASS_HOSTS') )
			return true;

		static $bypass_hosts = null;
		static $wildcard_regex = array();
		if ( null === $bypass_hosts ) {
			$bypass_hosts = preg_split('|,\s*|', WP_PROXY_BYPASS_HOSTS);

			if ( false !== strpos(WP_PROXY_BYPASS_HOSTS, '*') ) {
				$wildcard_regex = array();
				foreach ( $bypass_hosts as $host )
					$wildcard_regex[] = str_replace( '\*', '.+', preg_quote( $host, '/' ) );
				$wildcard_regex = '/^(' . implode('|', $wildcard_regex) . ')$/i';
			}
		}

		if ( !empty($wildcard_regex) )
			return !preg_match($wildcard_regex, $check['host']);
		else
			return !in_array( $check['host'], $bypass_hosts );
	}