Asked  7 Months ago    Answers:  5   Viewed   42 times

Basically, I'm trying to figure out how PHP can be called from a "web server".

I've read the documentation, but it didn't help much.

As far as I can tell, there are three ways to invoke PHP:

  • via command line (eg: php -f "/path/to/script.php")
  • via CGI(??) / via FastCGI (???)
  • via a web server (eg: Apache) module

So let's start with CGI. Maybe I'm just blind, but the spec doesn't mention how on Earth the web server passes data (headers & callbacks) to the thing implementing CGI. The situation is even worse with FastCGI.

Next up, we have server-specific modules, which, I don't even know what to search for since all leads end up nowhere.



Invoking a CGI script is pretty simple. PHP has a few peculiarities, but you basically only need to setup a list of environment variables, then call the PHP-CGI binary:

setenv SCRIPT_FILENAME=/path/to/script.php
setenv QUERY_STRING="id=123&name=title&parm=333"

exec /usr/bin/php-cgi

Most of them are boilerplate. SCRIPT_FILENAME is how you pass the actual php filename to the PHP interpreter, not as exec parameter. Crucial for PHP is also the non-standard variable REDIRECT_STATUS=200.

For a GET request you only need the environment variables. For a POST request, you simply pipe the HTTP request body as stdin to the executed php-cgi binary. The returned stdout is the CGI response consisting of an incomplete HTTP header, rnrn, and the page body.

(Just from memory. There maybe a few more gotchas.)

Wednesday, March 31, 2021
answered 7 Months ago

Which method of running PHP consumes less memory?

I assume that per PHP-processed request they are more or less the same. But if you have mod_php loaded into apache serving images too, then I assume your memory footprint will be higher due to serving static files.

Also which method consumes memory nearly constant. I see with mod_php my servers memory usage fluctuating between 300MB and 800MB, every few seconds.

You can make both pretty constant. If you carefully set MaxClients, MinSpareServers and MaxSpareServers, you pretty much can tell how many processes are running. If you also set memory_limit within your PHP config, you can calculate how much memory you need. You can do the same for fcgi too, since you can decide how many processes are running.

But with FastCGI, first response from server comes very late. I see with FastCGI there is an initial delay per webpage request. Once first response from server arrives, other items like images, css, js loads pretty faster.

This doesn't make sense. I am not sure why it happens in your case.

Is it OK to run mix of both? I have 5 sites on dedicated server. Is it ok if I run few with mod_php and rest with FastCGI?

I guess, but it will both be a nightmare to maintain and will probably be harder to configure for saving memory. Quite the contrary I believe.

I am sure that my server goes down mostly because of improper memory usage by mod_php. I checked all scripts. Is there any way to make sure memory consumption on server remains nearly constant?

Configure memory and processes as I outlined above, and keep monitoring.

Does complexity of .htaccess affects memory usage significantly? If yes, can it be a single reason to make server run out of memory?

I don't think so. per-directory .htaccess can slow things down, but unless there is some serious bug in Apache, it should not cause mass memory consumption.

Does apache MPM prefork/worker settings affect memory consumption? Do they affect mod_php and FastCGI mode equally?

It might, but I recommend to stay away from worker, as PHP is mostly not thread safe.

When I run "top" command, I see apache (httpd) consuming memory around 40MB. There are many instances of httpd running. Also in addition to that FastCGI forks some processes of similar size. What is normal memory size for httpd process?

30MB is the min. The upper limit depends on your application (I have seen cases where it was ~1GB)

As I am running Wordpress on all of our sites, which will be good way in that context?

It is probably a matter of taste. I have recently moved away from apache towards nginx+fastcgi. it takes a bit of time to get used to, but it does work well. No problems whatsoever with wordpress (even not with supercache, which is rather involved in terms of web server).

Does FastCGI/SuExec works fine with APC? Do I need to reconfigure APC to work with SuEXEC and FastCGI.

I am not using suExec, but fastcgi works well with APC. No need to configure anything.

Wednesday, March 31, 2021
answered 7 Months ago
$f = fopen("http://$username:$"); 

then just use the same methods as for manipulating files, eg. fread, fgets, fclose, etc.

Saturday, May 29, 2021
answered 5 Months ago

Okay, I managed to find the cause of the problem. It wasn't my code at all. It's PHP, it cannot spawn additional php-cgi's under Windows when running as FastCGI mode, under Linux it works perfectly, I simply pointed my server to my linux box IP and it had no problems with concurrent FCGI requests. Sucks, but I guess that's the way it is...

I did look deeper into the PHP source code after that and found that the section of code which responds to PHP_FCGI_CHILDREN has been encapsulated by #ifndef WIN32 So the developers must be aware of the issue

Wednesday, August 11, 2021
answered 3 Months ago

I worked around my original problem by using a different method. Here is what I do now:

  1. Write a temporary file with contents <?php include "< File to test >"; echo "OK"; ?>
  2. Generate the correct URL for the temporary file
  3. Perform HTTP request with this URL
  4. Check if result equals "OK". If yes, the file to test parses without errors.
  5. Delete temporary file

Maybe this could be done without the temporary file by issuing an HTTP request to the file to test directly. However, if there is a parse error and errors are suppressed, the output will be empty and not discernible from the output in the case of a file that gives no parse errors. This method is risky because the file is actually executed instead of just checked. In my case, there is only a limited number of users who have access to this functionality in the first place. Still, I'm naturally not entirely happy with it.

Why the exec() approach did not work, I still do not know exactly. pinaki might be right by suggesting to provide the full path to the PHP executable, but I cannot find out the full path.

Thank you everyone for answering, I upvoted you all. However, I cannot accept any of your answers as none of your suggestions really solved my problem.

Wednesday, August 18, 2021
Thomas Weller
answered 2 Months ago
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