Why doesn't PHP 7.2 fopen(/tmp, a) write to the file?

I found the file that didn't seem to be created:

1. PHP code: $fp = fopen ("/tmp/PHPDBG.txt", "a");

2. Expected location: /tmp/PHPDBG.txt.

3. Actual location: /tmp/systemd-private-c6f7629309e647818680f8a6ee1105d6-apache2.service-lGKGc6/tmp/PHPDBG.txt

Relevant links:

• Php has its own /tmp in /tmp/systemd-private-nABCDE/tmp when accessed through nginx

• Why PHP cannot see /tmp

So it sounds like this is some kind of systemd "feature" (Grrr!!!!). Which explains why it "used to work" (in previous versions of Apache, PHP and Linux).

Workaround

I edited /etc/systemd/system/multi-user.target.wants/apache2.service:

[Service]
...
PrivateTmp=true  <-- Changed this to "false"

Your condition is reversed: if (!$fp).

You are saying if not handle, then write to the file. It should be the opposite.

<?php
  function PHPDBG ($s) {
    $fp = fopen ("/tmp/PHPDBG.txt", "a");
    if ($fp) { // fixed condition.
      fputs($fp, $s . "\n");
      fclose($fp);
    } else {
      echo "<h3>FILE OPEN ERROR</h3>\n";
      echo "<p>" . print_r(error_get_last()) . "</p>\n";
      echo "<p>" . $php_errormsg . "</p>\n";
    }
  }

  PHPDBG('>>Hello');
  phpinfo();
  PHPDBG('<<Goodbye');
?>