Question

wp_re源代码_hints()

Prints re源代码 hints to browsers for pre-fetching, pre-rendering and pre-connecting to web sites.

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description

Gives hints to browsers to prefetch specific pages or render them in the background, to perform DNS lookups or to begin the connection handshake (DNS, TCP, TLS) in the background.

These performance improving indicators work by using <link rel"…">.

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源代码

File: wp-includes/general-template.php

function wp_re源代码_hints() {
	$hints = array(
		'dns-prefetch' => wp_dependencies_unique_hosts(),
		'preconnect'   => array(),
		'prefetch'     => array(),
		'prerender'    => array(),
	);

	/*
	 * Add DNS prefetch for the Emoji CDN.
	 * The path is removed in the foreach loop below.
	 */
	/** This filter is documented in wp-includes/formatting.php */
	$hints['dns-prefetch'][] = apply_filters( 'emoji_svg_url', 'https://s.w.org/images/core/emoji/2.3/svg/' );

	foreach ( $hints as $relation_type => $urls ) {
		$unique_urls = array();

		/**
		 * Filters domains and URLs for re源代码 hints of relation type.
		 *
		 * @since 4.6.0
		 *
		 * @param array  $urls          URLs to print for re源代码 hints.
		 * @param string $relation_type The relation type the URLs are printed for, e.g. 'preconnect' or 'prerender'.
		 */
		$urls = apply_filters( 'wp_re源代码_hints', $urls, $relation_type );

		foreach ( $urls as $key => $url ) {
			$atts = array();

			if ( is_array( $url ) ) {
				if ( isset( $url['href'] ) ) {
					$atts = $url;
					$url  = $url['href'];
				} else {
					continue;
				}
			}

			$url = esc_url( $url, array( 'http', 'https' ) );

			if ( ! $url ) {
				continue;
			}

			if ( isset( $unique_urls[ $url ] ) ) {
				continue;
			}

			if ( in_array( $relation_type, array( 'preconnect', 'dns-prefetch' ) ) ) {
				$parsed = wp_parse_url( $url );

				if ( empty( $parsed['host'] ) ) {
					continue;
				}

				if ( 'preconnect' === $relation_type && ! empty( $parsed['scheme'] ) ) {
					$url = $parsed['scheme'] . '://' . $parsed['host'];
				} else {
					// Use protocol-relative URLs for dns-prefetch or if scheme is missing.
					$url = '//' . $parsed['host'];
				}
			}

			$atts['rel'] = $relation_type;
			$atts['href'] = $url;

			$unique_urls[ $url ] = $atts;
		}

		foreach ( $unique_urls as $atts ) {
			$html = '';

			foreach ( $atts as $attr => $value ) {
				if ( ! is_scalar( $value ) ||
				     ( ! in_array( $attr, array( 'as', 'crossorigin', 'href', 'pr', 'rel', 'type' ), true ) && ! is_numeric( $attr ))
				) {
					continue;
				}

				$value = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );

				if ( ! is_string( $attr ) ) {
					$html .= " $value";
				} else {
					$html .= " $attr='$value'";
				}
			}

			$html = trim( $html );

			echo "<link $html />\n";
		}
	}
}

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更新日志

Version	description
4.6.0	Introduced.

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相关函数

Uses

• wp-includes/general-template.php: wp_dependencies_unique_hosts()
• wp-includes/general-template.php: wp_re源代码_hints
• wp-includes/formatting.php: emoji_svg_url
• wp-includes/http.php: wp_parse_url()
• wp-includes/formatting.php: esc_url()
• wp-includes/formatting.php: esc_attr()
• wp-includes/plugin.php: apply_filters()
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User Contributed Notes