CSC 107

Server-Side Scripting for the Web

Smith College > CS Dept > CSC 107 > Labs > PHP Files

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This lab will let you practice some file operations using PHP.

Part One: Displaying PHP Source

One difficult aspect of PHP is that unlike HTML and JavaScript, it is not easy to see the PHP source when you visit a page. Since the server has already interpreted the script, the original file can no longer be seen. For this part of the lab you will write a function that will take any file and display it in the browser as is, without any script or markup interpretation. You will test the script by calling your function on a few of the files you have created for previous labs -- both PHP and HTML sources.

Note that you might think it a good idea to create a more general PHP script, that could take an argument as from a form: viewfile.php?file=index.php. While this is easy to do, and would no doubt be useful, it is nonetheless not a good idea. Why? What files would be visible via this script?

Here's an outline of how the function can work:

1. You can read the file into an array using the file function.
2. Loop through the file and display the results. Make sure that you sanitize the output so that it is not interpreted as any HTML tags!
3. Wrap the whole thing in an HTML shell inside a <pre> tag.

There may be other ways to accomplish the same task. What else can you think of?

Part Two: Reading a Data File

For this exercise, we'll read a text file that contains a simple table of data, and format it for output. Normally we would want to store our data in a database rather than a text file, but sometimes this is impossible. For example the text file represents the output of some other program. In this case we will use the file /etc/printcap, which is produced automatically on Unix systems and lists information on the available printers. Here is what the file looked like when this lab was produced. (Note: if you want to try this lab on a non-unix computer, you can copy the content below into a text file and direct your script there.)

# This file was automatically generated by cupsd(8) from the
# /etc/cups/printers.conf file.  All changes to this file
# will be lost.
ford243|ford243:rm=beowulf.csc.smith.edu:rp=ford243:
burton_302|burton_302:rm=beowulf.csc.smith.edu:rp=burton_302:
burton_303|burton_303:rm=beowulf.csc.smith.edu:rp=burton_303:
burton_forum|burton_forum:rm=beowulf.csc.smith.edu:rp=burton_forum:
cats|cats:rm=beowulf.csc.smith.edu:rp=cats:
ford243_color|ford243_color:rm=beowulf.csc.smith.edu:rp=ford243_color:
ford321|ford321:rm=beowulf.csc.smith.edu:rp=ford321:
ford354|ford354:rm=beowulf.csc.smith.edu:rp=ford354:

Let's say we want to produce a list of the names of all the printers on the system. These are stored in the beginning of each line, up to the vertical pipe character |. (The first three lines are comments and should be ignored.) So you could do something like the following:

1. Read the file into an array of lines.
2. Loop through the array of lines. If the line is a comment, skip it. Otherwise, extract the part of the line that is the printer name and echo it.