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discover_pingback_server_uri › WordPress Function

Since1.5.0
Deprecatedn/a
discover_pingback_server_uri ( $url, $deprecated = '' )
Parameters: (2)
  • (string) $url URL to ping.
    Required: Yes
  • (string) $deprecated Not Used.
    Required: No
    Default: (empty)
Returns:
  • (string|false) String containing URI on success, false on failure.
Defined at:
Codex:

Finds a pingback server URI based on the given URL.

Checks the HTML for the rel="pingback" link and X-Pingback headers. It does a check for the X-Pingback headers first and returns that, if available. The check for the rel="pingback" has more overhead than just the header.


Source

function discover_pingback_server_uri( $url, $deprecated = '' ) {
	if ( ! empty( $deprecated ) ) {
		_deprecated_argument( __FUNCTION__, '2.7.0' );
	}

	$pingback_str_dquote = 'rel="pingback"';
	$pingback_str_squote = 'rel=\'pingback\'';

	/** @todo Should use Filter Extension or custom preg_match instead. */
	$parsed_url = parse_url( $url );

	if ( ! isset( $parsed_url['host'] ) ) { // Not a URL. This should never happen.
		return false;
	}

	// Do not search for a pingback server on our own uploads.
	$uploads_dir = wp_get_upload_dir();
	if ( str_starts_with( $url, $uploads_dir['baseurl'] ) ) {
		return false;
	}

	$response = wp_safe_remote_head(
		$url,
		array(
			'timeout'     => 2,
			'httpversion' => '1.0',
		)
	);

	if ( is_wp_error( $response ) ) {
		return false;
	}

	if ( wp_remote_retrieve_header( $response, 'X-Pingback' ) ) {
		return wp_remote_retrieve_header( $response, 'X-Pingback' );
	}

	// Not an (x)html, sgml, or xml page, no use going further.
	if ( preg_match( '#(image|audio|video|model)/#is', wp_remote_retrieve_header( $response, 'Content-Type' ) ) ) {
		return false;
	}

	// Now do a GET since we're going to look in the HTML headers (and we're sure it's not a binary file).
	$response = wp_safe_remote_get(
		$url,
		array(
			'timeout'     => 2,
			'httpversion' => '1.0',
		)
	);

	if ( is_wp_error( $response ) ) {
		return false;
	}

	$contents = wp_remote_retrieve_body( $response );

	$pingback_link_offset_dquote = strpos( $contents, $pingback_str_dquote );
	$pingback_link_offset_squote = strpos( $contents, $pingback_str_squote );
	if ( $pingback_link_offset_dquote || $pingback_link_offset_squote ) {
		$quote                   = ( $pingback_link_offset_dquote ) ? '"' : '\'';
		$pingback_link_offset    = ( '"' === $quote ) ? $pingback_link_offset_dquote : $pingback_link_offset_squote;
		$pingback_href_pos       = strpos( $contents, 'href=', $pingback_link_offset );
		$pingback_href_start     = $pingback_href_pos + 6;
		$pingback_href_end       = strpos( $contents, $quote, $pingback_href_start );
		$pingback_server_url_len = $pingback_href_end - $pingback_href_start;
		$pingback_server_url     = substr( $contents, $pingback_href_start, $pingback_server_url_len );

		// We may find rel="pingback" but an incomplete pingback URL.
		if ( $pingback_server_url_len > 0 ) { // We got it!
			return $pingback_server_url;
		}
	}

	return false;
}