使用RegEx从任意的内容中提取URLs。

function wp_extract_urls( $content ) {
	preg_match_all(
		"#(["']?)("
			. '(?:([w-]+:)?//?)'
			. '[^s()]+'
			. '[.]'
			. '(?:'
				. '([wd]+)|'
				. '(?:'
					. "[^`!()[]{}:'".,«»“”‘’s]|"
					. '(?:[:]d+)?/?'
				. ')+'
			. ')'
		. ")1#",
		$content,
		$post_links
	);

	$post_links = array_unique(
		array_map(
			static function( $link ) {
				// Decode to replace valid entities, like &.
				$link = html_entity_decode( $link );
				// Maintain backward compatibility by removing extraneous semi-colons (`;`).
				return str_replace( ';', '', $link );
			},
			$post_links[2]
		)
	);

	return array_values( $post_links );
}