get_search_form( bool $echo = true )

function get_search_form( $echo = true ) {
	/**
	 * Fires before the search form is retrieved, at the start of get_search_form().
	 *
	 * @since WP-2.7.0 as 'get_search_form' action.
	 * @since WP-3.6.0
	 *
	 * @link https://core.trac.wordpress.org/ticket/19321
	 */
	do_action( 'pre_get_search_form' );

	$format = current_theme_supports( 'html5', 'search-form' ) ? 'html5' : 'xhtml';

	/**
	 * Filters the HTML format of the search form.
	 *
	 * @since WP-3.6.0
	 *
	 * @param string $format The type of markup to use in the search form.
	 *                       Accepts 'html5', 'xhtml'.
	 */
	$format = apply_filters( 'search_form_format', $format );

	$search_form_template = locate_template( 'searchform.php' );
	if ( '' != $search_form_template ) {
		ob_start();
		require( $search_form_template );
		$form = ob_get_clean();
	} else {
		if ( 'html5' == $format ) {
			$form = '<form role="search" method="get" class="search-form" action="' . esc_url( home_url( '/' ) ) . '">
				<label>
					<span class="screen-reader-text">' . _x( 'Search for:', 'label' ) . '</span>
					<input type="search" class="search-field" placeholder="' . esc_attr_x( 'Search &hellip;', 'placeholder' ) . '" value="' . get_search_query() . '" name="s" />
				</label>
				<input type="submit" class="search-submit" value="'. esc_attr_x( 'Search', 'submit button' ) .'" />
			</form>';
		} else {
			$form = '<form role="search" method="get" id="searchform" class="searchform" action="' . esc_url( home_url( '/' ) ) . '">
				<div>
					<label class="screen-reader-text" for="s">' . _x( 'Search for:', 'label' ) . '</label>
					<input type="text" value="' . get_search_query() . '" name="s" id="s" />
					<input type="submit" id="searchsubmit" value="'. esc_attr_x( 'Search', 'submit button' ) .'" />
				</div>
			</form>';
		}
	}

	/**
	 * Filters the HTML output of the search form.
	 *
	 * @since WP-2.7.0
	 *
	 * @param string $form The search form HTML output.
	 */
	$result = apply_filters( 'get_search_form', $form );

	if ( null === $result )
		$result = $form;

	if ( $echo )
		echo $result;
	else
		return $result;
}