PHP, Filesystems and File I/O

One of the benefits of PHP being a server side scripting environment is that it gives the web developer easy access to the filesystem of the server on which the web server is running. This gives us the ability to create, open, delete, read and write files. We can also traverse the directory hierarchy of the server systems to do things like get directory listings and create new sub-directories.

In this chapter we will cover all aspects of interecting with files and the filesystem in details.

Opening and Creating Files in PHP

Existing files are opened, and new files created using the PHP fopen function. The fopen function accepts two arguments and returns a file handle which is subsequently used fo all future read and write interactions with that file. The first argument is the name (including the path) of the file to open. This path is relative to the server filesystem root, not your web server root. The second argument is an attribute indicating the mode in whcih you with to open the file (create, read only, write only etc). The following table lists the various file open attributes together with a broef description of each:

Mode	Description
r	Read only access. Pointer is positioned at start of file.
r+	Read and write access. Pointer is positioned at start of file.
w	Write only access. Pointer is positioned at start of file. File is created if it does not already exist.
w+	Read and write access. Pointer is positioned at start of file. File is created if it does not already exist.
a	Write only access. Pointer is positioned at end of file. File is created if it does not already exist.
a+	Read and write access. Pointer is positioned at end of file. File is created if it does not already exist.
x	Create and open for write only. Pointer is positioned at start of file. Return false if file already exists.
x+	Create and open for read and write. Pointer is positioned at start of file. Return false if file already exists.

Closing Files in PHP

Once a file has been opened it can closed using the fclose function. The fclose function takes a single argument; the file handle returned by the fopen function when the file was first opened.

Given this information we can write a script to open a file. For the purposes of this example we will create a new file in the root of our web server. We will open the file in w+ mode so that it will created if it does not already exist and provide both read and write access. We will then close the file using fclose():

<?php
$fileHandle = fopen('/tmp/php_essentials.txt', 'w+')
 OR die ("Can't open file\n");

fclose ($fileHandle);
?>

Writing to a File using PHP

Having created and opened the file the next task is to write data to the file. We can do this using the PHP fwrite and fputs functions. These are essentially tyhe same function so either can be used.

fwrite takes two arguments, the file handle returned form the orginal fopen and he string to be written. We can, therefore extend our example to write a string to our file:

<?php

?>$fileHandle = fopen('/tmp/php_essentials.txt', 'w+')
 OR die ("Can't open file\n");

fwrite ($fileHandle, "This line of text was written by PHP\n");
fclose($fileHandle);

After running the above script you should find a file exists on your server containing the line This line of text was written by PHP.