Locking files with PHP

Hello, I am just starting to use PHP. I have been using PERL for quite some time. I was wondering if there is any specific FILE LOCKING I need to implement to keep more than one person from altering a text file at the same time. For instance, in PERL, you use the flock command to set up an advisory file lock. Lets say that if I have a web page with a text based database, and more than one person wants to write to the file at the same time. In perl, if you use flock(FILE, 2). This causes person A to wait while person B writes to the file. flock(FILE, 8) unlocks the file. Then person A is allowed to write to the file. Does the perl equivalent of flock happen automatically in PHP? If not, how do you lock a file? Is it an advisory lock, or will it cause an error if two people try to access the same file at the same time for the same purpose (writing). Thanks, =========================== Matthew Toledo FrogNet Design & Domain Management design@frognet.net