1755 (<1)
spout v2.7.3 — Read and write spreadsheet files (CSV, XLSX and ODS), in a fast and scalable way
Similar Excel xlsx
775 (<1)
PHP_XLSXWriter — Lightwight XLSX Excel Spreadsheet Writer in PHP
Similar Excel xlsx
457 (<1)
spreadsheet-reader — A PHP spreadsheet reader (Excel XLS and XLSX, OpenOffice ODS, and variously separated text files) with a singular goal of getting the data out, efficiently
Similar Excel xlsx

Some additional repos to consider:
spreadsheet-parser — Fast XLSX parser that spares resources
xlsx-template-php — A library for templating of Excel Office documents. Supports MS Excel xlsx. Uses PHPExcel library.
XLSx — XLSx is a PHP library designed to manipulate the content of .xlsx files.
xlsx-reader — The project xlsx-reader is a PHP library for fast and efficient reading of XLSX spreadsheet files (e.g. generated by Microsoft Excel). It delivers functionality to efficiently read in data contained within the given XLSX file, also for very big XLSX files in the magnitude of multiple GBs.
excel-template — Replace variables in xlsx documents

Once a week...

... I send out a list of most interesting PHP libraries and apps.
Want to get it?