Empty php file displays "0"

[mafarriku]

Hi to all,
I've just came across a weird problem after changing hosting.
When a php file has no output (ajax actions or just empty php file) the output to the browser is '0'.

Is there a flag that controls this?
The php version is 5.2.17

Thank you very much!

[Weedpacket]

It's ringing some very distant bells for me, but not loudly enough for me to tell where they're coming from.

None of the code has changed? Do files that do produce output have the '0'?

Is the '0' really all that there is in the output? What is in the response headers?

Is it just empty PHP files (presumably that means "zero-length files with a .php extension") or does an empty .html file do it as well? What about a file that contains only a single space? Or just "[font=monospace]<?php[/font]"?

Is there anything given in php.ini for auto_prepend_file or auto_append_file?

What server are we talking about, here?

[mafarriku]

None of the code has changed? Do files that do produce output have the '0'?
No

Is the '0' really all that there is in the output? What is in the response headers?
Yes

Is it just empty PHP files (presumably that means "zero-length files with a .php extension") or does an empty .html file do it as well? What about a file that contains only a single space? Or just "<?php"?

Only files that produce no output, for instance:
"<?php ?>" will produce the 0
"<?php ?>&nbsp" will not produce the 0

Is there anything given in php.ini for auto_prepend_file or auto_append_file?
No

What server are we talking about, here?
Linux

Thank you very much.

[bradgrafelman]

How do you get from the empty PHP file to a browser? There are a few steps (and thus unknowns) in between.

For example, are you making a request to a webserver for this file? Which webserver are you using? How is PHP integrated with that webserver (e.g. which method does the webserver use to invoke the PHP interpreter when necessary... and how does it also determine when it is in fact necessary)?