PHP enables you to download file easily using built-in readfile() function. The readfile() function reads a file and writes it to the output buffer.
PHP readfile() function
$filename: represents the file name
$use_include_path: it is the optional parameter. It is by default false. You can set it to true to the search the file in the included_path.
$context: represents the context stream resource.
int: it returns the number of bytes read from the file.
PHP Download File Example: Text File
PHP Download File Example: Binary File