Are there specific caching mechanisms or techniques that could be causing conflicts with PHPExcel on the web server, leading to empty page outputs?

The empty page outputs in PHPExcel could be caused by conflicts with caching mechanisms or techniques on the web server. To solve this issue, you can try disabling any caching mechanisms that might interfere with PHPExcel's functionality, such as opcode caching or page caching.

// Disable opcode caching
ini_set('opcache.enable', 0);

// Disable page caching
header("Cache-Control: no-cache, must-revalidate");
header("Expires: Sat, 26 Jul 1997 05:00:00 GMT");