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PHP: Easy Dynamic Websites
<?php $total = 1 + 1; echo $total; ?>
Getting Started in PHP
There's a tradition in programming that the first thing you do
in any language is say 'Hello World'. Well, here's how you do
that in PHP. First of all, create a file in your server's root
directory called index.php. Put this text in it:
<?php echo "Hello World"; ?>
Let's look at this bit by bit. The first line means 'what
follows is PHP code'. 'echo' is the PHP command to send text to
the web browser, and each line of PHP has to end with a
semicolon. Finally, the last line means 'end of the PHP code'.
Now, the power of PHP is that those start and end tags can do
anywhere in a normal HTML document, as many times as you like.
For example:
my page - <?php echo date("m-d-Y"); ?>
This is a complete HTML document with pieces of embedded PHP.
The first PHP section inserts the date into the title, and the
second writes the answer to 1 + 1 (that's 2, you know) as the
content of the document - the word with a dollar before it is a
variable, storing the result of the sum. Where this all becomes
extremely useful is that your PHP code can open a connection to
a database, read data from it, and then the text into a
template, along with other things from the database like the
headline, the author's name and the date it was written.
Useful PHP Functions
Here's a quick reference of the most useful PHP functions to
help you get started.
date. This function returns the date in a format you specify
using letters. For example, date("D j M Y") outputs dates in
this format: Mon 1 Jan 2010.
echo. Writes text to the document. You can use <?= as a useful
shortcut for <?php echo.
explode. Divides up some text into an array by looking for
'seperator' letters or characters. Can be good if you're using
odd characters like | to separate data somewhere in your program.
fopen. Opens a file on your web server, but can also be used to
open a URL and so connect to another server.
fread. Reads the contents of the file, either all at once or
line by line.
header. Allows you to set your own HTTP headers - most often
used to control which MIME types things are sent with (the
content-type header), or to tell the browser whether to cache or
not (the cache-control header).
md5. Takes some text and produces a 'hash' using the MD5
algorithm. This is often used to allow checking of users'
passwords without needing to save their passwords in a database
in plain text. The sha1 function does the same thing, and is
more secure but slower.
mysql_connect. Connects to a MySQL server. You have to tell it
where the server is (usually localhost), as well as your
username and password.
mysql_select_db. Chooses which MySQL database to open on the
MySQL server you're connected to.
mysql_query. Sends any SQL commands you want to your MySQL
server.
mysql_fetch_assoc. Turns the results of a query sent to a MySQL
server into an array, to make it easier to use in your program.
str_replace. Replaces one word with another in some text. This
is useful when it comes to inserting the HTML tags between
paragraphs, for example.
strtotime. Turns an English-language description of a date and
time into a number representing that date and time (technically
known as a Unix timestamp). This makes them easier to use with a
database, as you can sort from the 'highest' (most recent) to
the 'lowest' (longest ago) more easily. You can convert back
from timestamps again by using the date function.
If you have trouble remembering the names of the PHP functions
(they're quite inconsistent), take a look at
http://www.ilovejackdaniels.com/php/php-cheat-sheet/ - this page
has a 'cheat sheet' with names of common functions that you can
print out and keep.
About the author:
Information supplied and written by Lee Asher of Eclipse Domain
Services
Domain Names, Hosting, Traffic and Email Solutions.