How do I find out the currently running PHP executable?

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

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