Resource Types
POSIX Functions
POSIX
PHP Manual

# Predefined Constants

The constants below are defined by this extension, and will only be available when the extension has either been compiled into PHP or dynamically loaded at runtime.

`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.
`POSIX_S_IFBLK` (integer)
  Block special file
`POSIX_S_IFCHR` (integer)
  Character special file
`POSIX_S_IFIFO` (integer)
  FIFO (named pipe) special file
`POSIX_S_IFREG` (integer)
  Normal file
`POSIX_S_IFSOCK` (integer)
  Socket

> Note:

> These constants are available since PHP 5.1.0. Please also note that some of them may not be available in your system.