Returns the current position of the file read/write pointer
ftell ( resource $handle ) : int
The file pointer must be valid, and must point to a file successfully opened by fopen() or popen(). ftell() gives undefined results for append-only streams (opened with "a" flag).
Returns the position of the file pointer referenced by handle as an integer; i.e., its offset into the file stream. If an error occurs, returns FALSE.
Note: Because PHP's integer type is signed and many platforms use 32bit integers, some filesystem functions may return unexpected results for files which are larger than 2GB.