WP_REST_URL_Details_Controller::get_document_head() WordPress Method

	private function get_document_head( $html ) {
		$head_html = $html;

		// Find the opening `<head>` tag.
		$head_start = strpos( $html, '<head' );
		if ( false === $head_start ) {
			// Didn't find it. Return the original HTML.
			return $html;
		}

		// Find the closing `</head>` tag.
		$head_end = strpos( $head_html, '</head>' );
		if ( false === $head_end ) {
			// Didn't find it. Find the opening `<body>` tag.
			$head_end = strpos( $head_html, '<body' );

			// Didn't find it. Return the original HTML.
			if ( false === $head_end ) {
				return $html;
			}
		}

		// Extract the HTML from opening tag to the closing tag. Then add the closing tag.
		$head_html  = substr( $head_html, $head_start, $head_end );
		$head_html .= '</head>';

		return $head_html;
	}