PHP 101 (part 5) - The Wonderland Factor (
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This concluding article in the series illustrates PHP's file
functions, with examples of how to read and write files on the system. It
also includes an explanation of user-defined functions, return values and
function arguments, together with some not-so-real-life examples.
If you've been following along, you already know how PHP can be used to extract
data from a database...it's as easy as apple pie. But in the real world, data
isn't always stored in neat rows and columns, and you're quite likely to come
across situations where the data you need is actually stored in a bunch of ASCII
text files.
You have three options here. You could con someone into the
mind-numbing task of inserting the textual data into a database. You could throw
up your hands in despair and look for another job. Or you could use PHP's
built-in file functions to extract and format the data.
The first option
requires guile and cunning. The second is unacceptable. And the third requires
this issue of PHP 101.
Over the next few pages, we'll be discussing the
basics of PHP's file functions, together with some interesting examples. And
then we'll explore the murky tunnels of user-defined functions, and delve deep
into the mysteries of local and global variables, return values and function
parameters. Pack some warm clothes, bring enough food and get someone to feed
the dogs - this is one journey you don't want to miss!{mospagebreak title=Windy
Nights} From the days of C, programmers have had the ability to create files on
the system, read them and perhaps even execute them via the shell. And, like all
good programming languages, PHP comes with a bunch of functions which allow you
to read and write files with minimum effort.
Let's get straight into the
nitty-gritty of reading a file. Create a text file and populate it with some
text - here's what our file, which we've named "random.txt", looks
like:
It was a dark and stormy evening. Outside the pub, the wind wailed and
moaned, singing dirges to long-lost sailors and making the timbers creak.
Inside, all was silent except for a brave nightlight that kept the ghosts
awake.
Oh, what I wouldn't give for a slug of ale just about now!
Before you can use PHP to read the contents of this file, you
need to ensure that you have permission to read it. On *NIX, this is
accomplished via the "chmod" command.- try
$ chmod 744 random.txt
to make it world-readable.
And here's some simple PHP
code that reads the file and returns the contents and file size:
<?php
// read file
$bytes = readfile("random.txt");
// display size
echo "<br>File is $bytes bytes in size.";
?>
And here's the output:
It was a dark and stormy night. Outside the pub, the wind wailed and
moaned, singing dirges to long-lost sailors and making the timbers creak.
Inside, all was silent except for a brave nightlight that kept the ghosts
awake. Oh, what I wouldn't give for a slug of ale just about now!
File is 286 bytes in size.
As you can see, readfile() doesn't do much - it simply reads
the file and displays the contents. It also returns the size of the file in
bytes - we've displayed this using an echo() above.
A far more useful
function, and one which lets you format the extracted data, is the file()
function, which allows you to read the file into a regular PHP array. Each
element of the array represents one line of the file, and therefore, the size of
the array is representative of the number of lines in the file. Take a look:
<?php
// set filename
$filename = "random.txt";
// read file into array
$contents = file($filename);
// get array length
$length = sizeof($contents);
echo "<b>File $filename contains $length line(s)</b><p>";
// display each line with "for" loop
for($counter=0; $counter<$length; $counter++)
{
echo "$contents[$counter]<br>";
}
?>
In this case, we've used the file() function to read the
contents of the entire file into an array called $contents. Using the sizeof()
function, we can obtain the length of the array, which is the same as the number
of lines present in the text file. The "for" loop is used to read and display
each element of the array.
And here's the output:
File random.txt contains 3 line(s)
It was a dark and stormy night. Outside the pub, the wind wailed and
moaned, singing dirges to long-lost sailors and making the timbers creak.
Inside, all was silent except for a brave nightlight that kept the ghosts
awake.
Oh, what I wouldn't give for a slug of ale just about now!
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