'require' files more than once

[Anon]

in c there's the if(!(defined)) function which lets you check whether or not a function has already been defined before you attempt to define or include it.

is there an equivalent in php? the nearest i could get to this was to place a constant at the top of each function, then check whether the constant had been defined.

thanks for any help
Rob

[dannys]

http://www.php.net/manual/en/function.function-exists.php

[rrijnders]

...or if your question is specifically about requiring files, another 2 second search produced:
<b>
http://www.php.net/manual/en/function.require-once.php
</b>