How do you know if a file is installed?

[ppowell]

I'm sorry, stupid question, but I am drawing a total blank.

How do I determine that a file in "/usr/bin/whatever" exists and can be executed using PHP?

Like for example, I have "gif2png" and I might not have yet done "make install" and I try to use gif2png and it will of course break because it's not there yet.

How do I determine beforehand that it's not there or not executable there or whatever?

Sorry, I'm dumb on this one.

Phil

[LordShryku]

[man]file_exists[/man] and [man]is_executable[/man]

[ppowell]

Wait, that's not what I was thinking about, I know about is_file and is_executable, but maybe what I'm looking for is the ability for PHP to use it internally.. after you install with "make install" you would reconfigure php.ini to allow for the usage of this program.

Phil