If you Get Info (command+I) on a .php file and click the Open With disclosure triangle you can associate that file with Excel; when you do that you can also choose to click the Change All button so that all .php files will open in Excel, including ones not sent from that source (CRM). You seem to want to open the files in Excel only if they're from that source, which OS X cannot easily do. Now if the OS selectively chose Excel for those CRM .php files, they must have been set with Excel's classic Mac OS creator code. Hope I've understood the issue and provided some assistance.