How do I find out the currently running PHP executable?

Question

From inside a PHP program I want to know the location of the binary executing it. Perl has $^X for this purpose. Is there an equivalent in PHP?

This is so it can execute a child PHP process using itself (rather than hard code a path or assume "php" is correct).

UPDATE

1. I'm using lighttpd + FastCGI, not Apache + mod_php. So yes, there is a PHP binary.
2. eval/include is not a solution because I'm spawning a server which has to live on beyond the request.

Things I've tried and don't work:

• $_SERVER['_'] looks like what I want from the command line but its actually from an environment variable set by the shell of the last executed program. When run from a web server this is the web server binary.
• which php will not work because the PHP binary is not guaranteed to be the same one as is in the web server's PATH.

Thanks in advance.

Answer 1

Yeah, $_SERVER['_'] is what you're talking about, or as near as exists. The reason you're getting a Web server binary when it's run from the web is that /usr/bin/php has nothing to do with the Web server's execution; what it's running is a separate SAPI. There's nothing from the web PHP instance to point to /usr/bin/php because there's no reason for there to be.

Answer 2

The PHP_BINDIR constant gives you the directory where the php binary is

Answer 3

The PHP_BINDIR constant is probably the easiest thing to use; the next best thing I could come up with is basically re-creating that bindir path from the extension_dir configuration setting:

$phpbin = preg_replace("@/lib(64)?/.*$@", "/bin/php", ini_get("extension_dir"));

It has a regex in it, so it feels more like your native perl(!) but otherwise is not especially optimal.

Answer 4

In PHP5.4 you can use the PHP_BINARY constant, it won't work via mod_php or similar but will via CGI etc.

For earlier versions of PHP readlink('/proc/self/exe'); will probably be fine, again it won't work via mod_php.