PHP Error “Unknown: failed to open stream… in Unknown on line 0…” when editing php files

I get a strange php error:

2022-03-14 10:52:19: (mod_fastcgi.c.421) FastCGI-stderr: PHP message: 
PHP Warning:  Unknown: failed to open stream: 
No such file or directory in Unknown on line 0
PHP message: PHP Fatal error:  Unknown: Failed opening required 
'var/www/vhosts/webdev/sites/test/hello.php'
(include_path='.') in Unknown on line 0

Long explanation:

1. I create a file hello.php in my webroot, having the content:

   <?php echo("hello"); ?>

2. I run this file in a browser, all is fine, it shows “hello”

3. Now I edit this file so the content now is:

   <?php echo("hello"); echo("world"); ?>

4. I run this edited file in a browser => The error is shown

5. I reload the page (F5 or ctrl-R) => all is working fine now

In other words: Whenever I edit a php file and try to run it in a browser, I get this error message. After reloading the page it works!

That is the real strange thing, after reloading everything is working fine!!!

My config

• a local raspberry pi running raspbian

• webserver: lighttpd (standard install from repo)

• php7.3-fpm (standard install from repo)

• all file permissions in my web dev folder are 775, all files are www-data:www-data owned

• NO selinux running (like in other answers suggested)

• the php.ini is pretty much untouched, some options:

  auto_prepend_file = 
   auto_append_file = 
   include_path = "."

• there are no other hidden config files in the folder

With html files there are no problems. So it must be a php-fpm problem. I am out of ideas now. It might be a very easy fix, but I am not a Pro.

Any ideas how to fix this?

Answer

In the error log, the path doesn’t start with a slash “/”

var/www/vhosts/webdev/sites/test/hello.php

which indicates a misconfiguration in lighttpd/fastcgi configuration

Fixing the path should make everything work correctly.