Magento 1: Check if H1 tag is existing on the product description. The client wants to add the H1 tag on the description in the certain products (magento backend). Change H1 to H2 in the page title if H1 found on the description.

check-if-h1-existing.php

<?php $product_description = $_helper->productAttribute($_product, $_product->getDescription(), 'description'); ?>

<?php if( strstr($product_description, '<h1') ) : // Check if H1 tag exists on the description ?>
 <div class="page-title"> 
    <h2 class="h1-page-title h1-title-exists-on-description">
        <?php echo $_helper->productAttribute($_product, $_product->getName(), 'name'); ?>
    </h2>
</div><!--/.page-title --> 
<?php else: // Check if H1 tag exists on the description ?>
 <div class="page-title">  
    <h1 class="h1-title-NOT-found-on-description" itemprop="name">
        <?php echo $_helper->productAttribute($_product, $_product->getName(), 'name'); ?>
    </h1>
  </div><!--/.page-title --> 
  <?php endif; // Check if H1 tag exists on the description ?>