This function gets the inode of a file. It returns you the inode number which is unique for each file in the system. For Unix file systems only. Works for directories too.

Basically, a file’s inode stores meta data of the file. See this Wikipedia entry on inode for more information.

The results of this function are cached - see clearstatcache()

$inode = fileinode( 'output.txt' ); // 1875969