php 7.2

My site was running fine and dandy for a few years.  I made the necessary adjustments to make it compatible with PHP 7.2 and upgraded the server.  A few days later I started receiving random 502 errors.

The problem apparently was a simple else if statement within a WordPress filter.  Here is the important parts of the code:

function php72_killer() {
  for($hour = 8; $hour < 17; $hour++) :
    $display_hour = $hour;
    $ampm = 'am';
    if ( $hour == 0 ) {
      $display_hour = 12;
    }
    else if ( $hour > 12 ) {
      $display_hour = $hour - 12;
      $ampm = 'pm';
    }
    else if ($hour==12) {
      $ampm = 'pm';
    }
  endfor;
}
add_meta_box( 'some_id', 'Section Title', 'php72_killer', 'post_type', 'normal' );

That last else if turned out to be the problem?  Why?  I don’t fully understand, but I found PHP 7.2 introduced optimized else ifs:  https://derickrethans.nl/php7.2-switch.html

It’s important to note that this for loop with if-statements outside of the WordPress callback doesn’t cause random 502 errors.

So what fixed my 502 errors?  not having a 2nd else if:

function php72_killer() {
  for($hour = 8; $hour < 17; $hour++) :
    $display_hour = $hour;
    $ampm = 'am';
    if ( $hour == 0 ) {
      $display_hour = 12;
    }
    else if ( $hour > 12 ) {
      $display_hour = $hour - 12;
      $ampm = 'pm';
    }
    if ($hour==12) {
      $ampm = 'pm';
    }
  endfor;
}
add_meta_box( 'some_id', 'Section Title', 'php72_killer', 'post_type', 'normal' );

Go figure.