How to get a string from C library into PHP via SWIG?

I have a need to call a C language function from a PHP script. The function, which I wrote, looks like this: /* * foo(): Takes a string in sIn and writes another string into sOut according to what is passed in, and the * value at *pcch. Will not write more than *pcch bytes to output, including null terminator. * Upon return, *pcch contains number of chars written to sOut. */ void foo(const char * sIn, char * sOut, size_t * pcch); So basically I need to pass down a string, and get back a string. I have been using swig but clearly I ain't getting it (I am good in C but new to PHP). Lots of warnings, crashes, and so on. No happiness. The swig docs show how to pass strings between python, java, etc., and C, but nothing on C <---> PHP. Can anyone help me with a fragment of sample code, or a link? Thanks Eric