file_get_contents Not allowed??

I’m using file_get_contents in a theme development (in a widget of the theme). However the theme check plugin gives me following warning:

WARNING: file_get_contents was found in the file file.php possible file operations.

Line 49: $data = file_get_contents ( 'https://example.com');
Line 62: $count= file_get_contents ( $cfile );

My question is that if it is not allowed in the themes, is there any alternative for this function which can be used?
Thanks.