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WP_oEmbed::discover( string $url )

Attempts to discover link tags at the given URL for an oEmbed provider.

Parameters

$url

(string) (Required) The URL that should be inspected for discovery <link> tags.

Return

(string|false) The oEmbed provider URL on success, false on failure.

Source

File: wp-includes/class-wp-oembed.php 

public function discover( $url ) {
		$providers = array();
		$args      = array(
			'limit_response_size' => 153600, // 150 KB
		);

		/**
		 * Filters oEmbed remote get arguments.
		 *
		 * @since 4.0.0
		 *
		 * @see WP_Http::request()
		 *
		 * @param array  $args oEmbed remote get arguments.
		 * @param string $url  URL to be inspected.
		 */
		$args = apply_filters( 'oembed_remote_get_args', $args, $url );

		// Fetch URL content.
		$request = wp_safe_remote_get( $url, $args );
		$html    = wp_remote_retrieve_body( $request );
		if ( $html ) {

			/**
			 * Filters the link types that contain oEmbed provider URLs.
			 *
			 * @since 2.9.0
			 *
			 * @param string[] $format Array of oEmbed link types. Accepts 'application/json+oembed',
			 *                         'text/xml+oembed', and 'application/xml+oembed' (incorrect,
			 *                         used by at least Vimeo).
			 */
			$linktypes = apply_filters(
				'oembed_linktypes',
				array(
					'application/json+oembed' => 'json',
					'text/xml+oembed'         => 'xml',
					'application/xml+oembed'  => 'xml',
				)
			);

			// Strip <body>.
			$html_head_end = stripos( $html, '</head>' );
			if ( $html_head_end ) {
				$html = substr( $html, 0, $html_head_end );
			}

			// Do a quick check.
			$tagfound = false;
			foreach ( $linktypes as $linktype => $format ) {
				if ( stripos( $html, $linktype ) ) {
					$tagfound = true;
					break;
				}
			}

			if ( $tagfound && preg_match_all( '#<link([^<>]+)/?>#iU', $html, $links ) ) {
				foreach ( $links[1] as $link ) {
					$atts = shortcode_parse_atts( $link );

					if ( ! empty( $atts['type'] ) && ! empty( $linktypes[ $atts['type'] ] ) && ! empty( $atts['href'] ) ) {
						$providers[ $linktypes[ $atts['type'] ] ] = htmlspecialchars_decode( $atts['href'] );

						// Stop here if it's JSON (that's all we need).
						if ( 'json' === $linktypes[ $atts['type'] ] ) {
							break;
						}
					}
				}
			}
		}

		// JSON is preferred to XML.
		if ( ! empty( $providers['json'] ) ) {
			return $providers['json'];
		} elseif ( ! empty( $providers['xml'] ) ) {
			return $providers['xml'];
		} else {
			return false;
		}
	}

Uses

Uses Description
wp-includes/class-pop3.php: stripos()
wp-includes/class-wp-oembed.php: oembed_remote_get_args

Filters oEmbed remote get arguments.
wp-includes/http.php: wp_safe_remote_get()

Retrieve the raw response from a safe HTTP request using the GET method.
wp-includes/http.php: wp_remote_retrieve_body()

Retrieve only the body from the raw response.
wp-includes/shortcodes.php: shortcode_parse_atts()

Retrieve all attributes from the shortcodes tag.
wp-includes/class-wp-oembed.php: oembed_linktypes

Filters the link types that contain oEmbed provider URLs.
wp-includes/plugin.php: apply_filters()

Calls the callback functions that have been added to a filter hook.

Used By

Used By Description
wp-includes/class-wp-oembed.php: WP_oEmbed::get_provider()

Takes a URL and returns the corresponding oEmbed provider’s URL, if there is one.

Changelog

Version Description
2.9.0 Introduced.

© 2003–2019 WordPress Foundation
Licensed under the GNU GPLv2+ License.
https://developer.wordpress.org/reference/classes/wp_oembed/discover