How to use PHP to find hte presence or absent of the file???

Hi ya all! I'm trying to figure out how to use the PHP script to detect the presence or absent of the file. I'm using UNIX machine, so it is not a problem. I do not want to use the fopen() to open the file since it is not a readable file, but a executable file. I'm thinking of using the exec() function to list hte file and return true if the file is there. exec("ls -la test.exe"); The only problem is how to tell? Anyone know? Thanks! Scott