Emoji-css-builder is a project mainly written in PHP, it's free.
$ php emoji.php --width=15 --height=15 --css=1--width=15 - icon width--height=15 - icon height--alias=default - used in sprite file name and css classes--css=1 - generate css. values 0 or 1--json=1 - generate json file. values 0 or 1--result_dir=... - directory with results of script work--xml_file=... - path to emoji config file