There may be times when you don't want to store information in a database and may want to work directly with a file instead. An example is a logfile that tracks when your application can't connect to the database. It'd be impossible to keep this information in the database, since it's not available at exactly the time you'd need to write to it. PHP provides functions for file manipulation that can perform the following:
Check the existence of a file
Create a file
Append to a file
Rename a file
Delete a file
We've already discussed the include and require functions for pulling information directly into a PHP script. At this junction, we'll focus on working with file content.
Since working directly with files from your PHP code can create security risks, it's a good idea to find solutions to problems that don't use files directly if possible; for example, storing information in a database instead of file. You must be very careful to not allow misuse of your PHP programs to either read or destroy the contents of important files either accidentally or as part of an attack.
To check for the existence of a file, use the function file_exists,
which takes the name of the file to check for its parameter, as shown in Example 11-20. If the file exists, it returns TRUE; otherwise, it returns FALSE.
Example 11-20. The file_exists.php script checks to see if the file is there
<?php $file_name="file_exists.php"; if(file_exists($file_name)) { echo ("$file_name ...No credit card required