&reftitle.constants; &extension.constants;

`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

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