Thanks for the reply. I have built a small flat file CMS that creates new pages using a password protected form. Each 'page' consists of a text file (the content) and a .php file (the output script). It has worked well for me for a number of years. However, the CMS is available to anyone who wants to download the scripts. I have seen some examples of websites other people have created with my system but I have no way of knowing whether it is reliable on all servers (Apache only). In other words, will the system work for everyone?
I hope that explains the reason for the question. I was wondering if 'touch', 'fwrite' etc can write any type of file in addition to text files and to what extent some Apache servers might impose restrictions on writing certain types. One example is .htaccess.