title: Warning: Use of undefined constant _ - assumed '_' (this will throw an Error in a future version of PHP) after updating to PHP 7.2
body: <p>I have checked the other related posts but unfortunately it didn't help my issue. </p>
  
  <p>I am getting </p>
  
  <blockquote>
    <p>Warning: Use of undefined constant _ - assumed '_' (this will throw an Error in a future version of PHP)</p>
  </blockquote>
  
  <p>error after updating to PHP version 7.2</p>
  
  <p>I traced the reason to this code snippet: </p>
  
  <pre><code>&lt;span class="post-container__excerpt-price"&gt;&lt;?php echo '$' . number_format( (float)get_field('price', $post-&gt;ID) );  ?&gt;&lt;/span&gt;
  </code></pre>
  
  <p>When I remove this the error goes away but I can't seem to find any glaring issues with this code either. <code>'price', $post-&gt;ID</code> is referring to a custom field that is created with ACF.</p>
  
  <p>Anyone has any idea?
  Thanks a lot!</p>
  
  <p>The entire code block is below:</p>
  
  <pre><code>// create shortcode to list all listings
  add_shortcode( 'list-posts-basic', 'rmcc_post_listing_shortcode1' );
  function rmcc_post_listing_shortcode1( $atts ) {
      ob_start();
      $query = new WP_Query( array(
          'post_type' =&gt; 'listings',
          'posts_per_page' =&gt; -1,
          'order' =&gt; 'DESC',
          'orderby' =&gt; 'date',
      ) );
      if ( $query-&gt;have_posts() ) { ?&gt;
          &lt;div class="posts-container"&gt;
              &lt;?php while ( $query-&gt;have_posts() ) : $query-&gt;the_post(); ?&gt;
              &lt;div class="post-container" id="post-&lt;?php the_ID(); ?&gt;" &lt;?php post_class(); ?&gt;&gt;
  
                  &lt;a class="" href="&lt;?php the_permalink(); ?&gt;"&gt;&lt;div class="listing-post-img" style="background: url(&lt;?php echo get_the_post_thumbnail_url() ?&gt; )"&gt;&lt;/div&gt;&lt;/a&gt;
  
                  &lt;div class="post-container__content"&gt;
                      &lt;a href="&lt;?php the_permalink(); ?&gt;"&gt;&lt;h3&gt;&lt;?php the_title(); ?&gt;&lt;/h3&gt;&lt;/a&gt;
                      &lt;p class="post-container__excerpt"&gt;
                          &lt;?php the_excerpt();  ?&gt;
                          &lt;span class="post-container__excerpt-price"&gt;&lt;?php echo '$' . number_format( (float)get_field('price', $post-&gt;ID) );  ?&gt;&lt;/span&gt;
                      &lt;/p&gt;
  
                      &lt;a class="post-container__button" href="&lt;?php the_permalink(); ?&gt;"&gt;View Details&lt;/a&gt;
                  &lt;/div&gt;
              &lt;/div&gt;
              &lt;?php endwhile;
              wp_reset_postdata(); ?&gt;
          &lt;/div&gt;
      &lt;?php $myvariable = ob_get_clean();
      return $myvariable;
      }
  }
  </code></pre>