I have not implemented any below solutions. But I think the first reference is good
References:
- https://blog.bitexpert.de/blog/think-about-it-phpexcel-performance-tweaks-part-1/
- http://stackoverflow.com/questions/4817651/phpexcel-runs-out-of-256-512-and-also-1024mb-of-ram
- PHPOffice/PHPExcel#420
- https://github.com/PHPOffice/PHPExcel/blob/develop/Documentation/markdown/Overview/04-Configuration-Settings.md