Predefined Constants
posix_mknod constants
Predefined Constants
PHP Manual

## posix_access() constants

> Note:

> These constants are available starting with PHP 5.1.0. Please note that some of them may not be available on your system.

`POSIX_F_OK` (integer)
  Check whether the file exists.
`POSIX_R_OK` (integer)
  Check whether the file exists and has read permissions.
`POSIX_W_OK` (integer)
  Check whether the file exists and has write permissions.
`POSIX_X_OK` (integer)
  Check whether the file exists and has execute permissions.

Predefined Constants
posix_mknod constants
Predefined Constants
PHP Manual