Path to the file.
Note that mode is not automatically assumed to be an octal value, so strings (such as "g+w") will not work properly. To ensure the expected operation, you need to prefix mode with a zero (0):
chmod("/somedir/somefile", 755); // decimal; probably incorrect
chmod("/somedir/somefile", "u+rwx,go+rx"); // string; incorrect
chmod("/somedir/somefile", 0755); // octal; correct value of mode
The mode parameter consists of three octal number components specifying access restrictions for the owner, the user group in which the owner is in, and to everybody else in this order. One component can be computed by adding up the needed permissions for that target user base. Number 1 means that you grant execute rights, number 2 means that you make the file writeable, number 4 means that you make the file readable. Add up these numbers to specify needed rights. You can also read more about modes on Unix systems with 'man 1 chmod' and 'man 2 chmod'.
// Read and write for owner, nothing for everybody else
// Read and write for owner, read for everybody else
// Everything for owner, read and execute for others
// Everything for owner, read and execute for owner's group
The current user is the user under which PHP runs. It is probably not the same user you use for normal shell or FTP access. The mode can be changed only by user who owns the file on most systems.
This function will not work on remote files as the file to be examined must be accessible via the servers filesystem.
When safe mode is enabled, PHP checks whether the files or directories you are about to operate on have the same UID (owner) as the script that is being executed. In addition, you cannot set the SUID, SGID and sticky bits.