Intro to PHP
Example
- "Hello
world" in HTML
1:<html>
2: <head>
3:
<title>Hello, World</title>
4:
</head>
5:
6: <body>
7: Hello World!
8:
</body>
9:</html>
In the case of a PHP page the
HTML that a browser receives is partly generated when the request for the page
occurs. This is why these and CFML pages are called "dynamic."
- "Hello
world" in PHP:
Here is a similar page, this time relying on PHP to
create some of the output that will be sent
to the browser:
1:<html>
2:
<head>
3: <title>Hello, World</title>
4: </head>
5:
6:
<body>
7: <?php echo "Hello World from PHP!"; ?>
8:
</body>
9:</html>
Example 2
View the output: hello_world.php
There are a couple of important things to
note about Example
2 . First, the
document has the extension ".php" - this is what tells the HTTP
server to hand over processing of this page to the PHP engine.
Nevertheless, most of the file is still processed exactly is if it
were ordinary HTML. The exception is line #7. Here there is some PHP
code, located between
<?php
and
?>
These tags turn "on" and "off" processing of the document as PHP -
outside of these tags the document is treated like normal HTML and
is sent directly to the client's browser. Inside of these tags the
file is processed as PHP code. The code is executed and the output
is built into the document.
Line #7 relies
on the PHP echo() function to create output almost identical to that of Example
1. Note as we said that print() does essentially the same thing.
- Inside-out languages
PHP and other modern web
programming languages (such as CFML) can be
mixed with, or "embedded" into, normal HTML. Because code ends
up getting inserted into HTML-like files (as opposed to generating
HTML from scratch)
languages like PHP are referred to as "inside out".
- But is this dynamic?
- This page might not seem truly dynamic, because it will always produce the same output. PHP of course can interact with a database as we did with CFML so that the content changes as the date does. Also, the following simple PHP program which prints out the
current date and time will have content that is dynamic as well:
- Today's date
in PHP
1:<html>
2:
<head>
3: <title>PHP Date
Example</title>
4: </head>
5:
6:
<body>
7: <?php
8:
9: echo "Hello again from
PHP!";
10: echo "<br>";
11: echo "It is now: ";
12: echo date ("l dS of
F Y h:i:s A");
13:
14: ?>
15: </body>
16:</html>
Example 3
View the output: simple_date.php
There are two things to note about Example
3 ... First, on
line #10 an HTML tag is sent as part of the text coming from PHP.
This illustrates how HTML can live either
outside the PHP tags, or inside: if inside then it needs to be
dynamically created by something like the echo() function.
On line #12 the PHP date() function is called, which returns a string corresponding to
the current date/time on the sever at the moment the page output is generated. This content is not
only technically dynamic but also results in unique output each time
the page is requested.
The string ("l dS of F Y h:i:s
A") that is passed into the date() function tells PHP what date format to use for the output.
A. Set up a bookmark or get a
local copy of the official PHP
documentation
PHP Manual - http://www.php.net/manual/en
To quickly look up any PHP
command (function), open the
manual in a
browser window, enter the name of the function into the search box
and hit enter .
A Basic
Tutorial - http://www.php.net/tut.ph
History of PHP - http://www.php.net/history
There is also a page in the online
manual comparing PHP with some other languages:
http://www.php.net/manual/en/faq.languages.php
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