Powerful as it is, MySQL is not the only (or necessarily the best) way to store all data on a web server. Sometimes it can be quicker and more convenient to directly access files on the hard disk. Cases in which you might need to do this are modifying images such as uploaded user avatars, or log files that you wish to process.
First, though, a note about file naming. If you are writing code that may be used on various PHP installations, there is no way of knowing whether these systems are case-sensitive. For example, Windows and Mac OS X filenames are not case-sensitive, but Linux and Unix ones are. Therefore you should always assume that the system is case-sensitive and stick to a convention such as all lowercase filenames.
To determine whether a file already exists, you can use the
file_exists function, which returns
FALSE, and is used like this:
if (file_exists("testfile.txt")) echo "File exists";
At this point testfile.txt doesn’t exist, so let’s create it and write a few lines to it. Type in Example 7-4 and save it as testfile.php.
<?php // testfile.php $fh = fopen("testfile.txt", 'w') or die("Failed to create file"); $text = <<<_END Line 1 Line 2 Line 3 _END; fwrite($fh, $text) or die("Could not write to file"); fclose($fh); echo "File 'testfile.txt' written successfully"; ?>
When you run this in a browser, all being well, you will receive the message “File ‘testfile.txt’ ...