Certainly, yes. Check out the PHP documentation on fopen(), fclose(), fread(), and fwrite(). Those will tell you what you need.
I do suggest that, however, you look into using a database for this type of application. In the long run, it will make your job easier, faster, and the script will be more scalable and the database more easily maintained, too.
For starters, check out MySQL.com, and then get phpDBAdmin from php.resourceindex.com
That'll make your job a lot easier.