Allowed tags for H1 page title in Wordpress

page_titles.php

<?php function slug_page_titles() {
	if(function_exists('get_field')) {

		if($on_page_title) { ?>
			<header class="entry-header">
				<h1 class="entry-title">
					<?php echo wp_kses(
						$on_page_title,
						array(
							'span' => array(),
							'em' => array(),
              'strong' => array(),
              'br' => array(),
						)
          );
          ?>
				</h1>
			</header><!-- .entry-header -->
		<?php } else { ?>
			<header class="entry-header">
				<?php the_title( '<h1 class="entry-title">', '</h1>' ); ?>
			</header><!-- .entry-header -->
		<?php }
	}
}