How to count files in a directory using PHP?

PHP contains many functions like count(), iterator_count(), glob(), openddir(), readdir(), scandir() and FilesystemIterator() to count number of files in a directory.
count() Function: The count() functions is an array function which is used to count all elements in an array or something in an object. This function uses COUNT_RECURSIVE as a mode to recursively count the array that is useful for counting all the elements of a multidimensional array.
Syntax: 

int count( mixed $array_or_countable, int $mode = COUNT_NORMAL )

glob() Function: The glob() function is a Filesystem function that searches all possible pathnames matching pattern according to the rules used by the libc glob() function.
Syntax:  

glob( string $pattern, int $flags = 0 )

Program 1: This program uses glob() and count() function to count all files within the directory.  

Output: 

20 files

openddir() Function: The openddir() function is used to open a directory handle. The path of the directory to be opened is sent as a parameter to the opendir() function and it returns a directory handle resource on success, or FALSE on failure.
Syntax:  

opendir( string $path, resource $context )

readdir() Function: The readdir() function is a directory function which reads the entries from directory handle those are returned in the order in which they are stored by the filesystem.
Syntax:  

readdir( resource $dir_handle )

Program 2: This program uses openddir() and readdir() function to count all files within the directory. 

Output: 

20 files

scandir() Function: The scandir() function is used to return an array of files and directories of the specified directory. The scandir() function lists the files and directories which are present inside a specified path.
Syntax:  

scandir( string $directory, int $sorting_order = SCANDIR_SORT_ASCENDING, resource $context )

Program 3: This program uses scandir() and count() function to count all files within the directory. 

Output: 

20 files

FilesystemIterator() Function: The FilesystemIterator::__construct() function is used to create a new filesystem iterator from the path.
Syntax:  

FilesystemIterator::__construct( string $path, 
      int $flags = FilesystemIterator::KEY_AS_PATHNAME 
      | FilesystemIterator::CURRENT_AS_FILEINFO 
      | FilesystemIterator::SKIP_DOTS )

iterator_count() Function: The iterator_count() function is SPL is used to count the iterator elements.
Syntax:  

int iterator_count( $iterator )

Program 4: This program uses FilesystemIterator() and iterator_count() function to count all files within the directory.

Output:  

20 files