PHP_OS - does it contain OS it was built on or runs on?

Question

I searched for quite a while now, but i could not find a definite answer to the question wether the constant PHP_OS contains the OS php was built on or runs on. The php documentation of php_uname (http://php.net/manual/de/function.php-uname.php) states: "For the name of just the operating system, consider using the PHP_OS constant, but keep in mind this constant will contain the operating system PHP was built on. " However, on the very same page there is a comment from 2006 stating: "Contrary to the last note, PHP_OS does display the OS PHP runs on currently, [...] This has nothing to do with the system PHP was built on." I could not find any definite answer anywhere on the web regarding this question (topis about php_uname and PHP_OS mostly only cover os detection and similar topics). What's right now - the documentation or the comment? The pear-core package uses PHP_OS to determine wether it's running on Unix-like systems or on windows, so is it safe to assume the documentation is i…

Accepted Answer

I had a look at the source code. The configure script does this:

```
PHP_OS=`uname | xargs`
AC_DEFINE_UNQUOTED(PHP_OS,"$PHP_OS",[uname output])
```

and then `main.c` does this:

```
char *php_os;
php_os=PHP_OS;
REGISTER_MAIN_STRINGL_CONSTANT("PHP_OS", php_os, strlen(php_os), CONST_PERSISTENT | CONST_CS);
```

which means that `PHP_OS` in PHP is what was in `php_os` in the C code, which is what was #defined by the header file constructed by the configure script, which is determined by running `uname` at configuration time.

So, it's the system you were built on, not the system you were running on.

There's some special-cased code for Windows: `main.c` sets `php_os` to `"WINNT"` if `WIN32` is defined. But, again, this is at build time, not at run time, even if you manage to compile on Unix and run on Windows or vice versa.

PHP_OS - does it contain OS it was built on or runs on?

Solution

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