The colours you see are just a visual aid to make it easier to see the PHP tags and the different parts of a PHP expression. Note also that this is not like a CGI script. The file does not need to be executable or special in any way. Think of it as a normal HTML file which happens to have a set of special tags available to you that do a lot of interesting things.
<html><head><title>PHP Test</title></head>
<body>
<?php echo "Hello World<P>"; ?>
</body></html>
This program is extremely simple and you really didn't need to use PHP to create a page like this. All it does is display: Hello World
If you tried this example and it didn't output anything, chances are that the server you are on does not have PHP enabled. Ask your administrator to enable it for you.
The point of the example is to show the special PHP tag format. In this example we used <?php to indicate the start of a PHP tag. Then we put the PHP statement and left PHP mode by adding the closing tag, ?>. You may jump in and out of PHP mode in an HTML file like this all you want.
For the browser that you are using right now to view this page, this displays:
<?php echo $HTTP_USER_AGENT; ?>
Mozilla/2.0 (compatible; MSIE 3.01; Windows 95)There are many other variables that are automatically set by your web server. You can get a complete list of them by creating a file that looks like this:
Then load up this file in your browser and you will see a page full of information about PHP along with a list of all the variables available to you.
<?php phpinfo()?>
You can put multiple PHP statements inside a PHP tag and create little blocks of code that do more than just a single echo. For example, if we wanted to check for Internet Explorer we could do something like this:
Here we introduce a couple of new concepts. We have an "if" statement. If you are familiar with the basic syntax used by the C language this should look logical to you. If you don't know enough C or some other language where the syntax used above is used, you should probably pick up any introductory C book and read the first couple of chapters. All the tricky string and memory manipulation issues you have to deal with in C have been eliminated in PHP, but the basic syntax remains.
<?php
if(strstr($HTTP_USER_AGENT, "MSIE")) {
echo "You are using Internet Explorer<br>";
}
?>
The second concept we introduced was the strstr() function call. strstr() is a function built into PHP which searches a string for another string. In this case we are looking for "MSIE" inside $HTTP_USER_AGENT. If the string is found the function returns true and if it isn't, it returns false. If it returns true the following statement is executed.
We can take this a step further and show how you can jump in and out of PHP mode even in the middle of a PHP block:
Instead of using a PHP echo statement to output something, we jumped out of PHP mode and just sent straight HTML. The important and powerful point to note here is that the logical flow of the script remain intact. Only one of the HTML blocks will end up getting sent to the viewer. Running this script right now results in:
<?php
if(strstr($HTTP_USER_AGENT, "MSIE")) {
?>
<center><b>You are using Internet Explorer</b></center>
<?
} else {
?>
<center><b>You are not using Internet Explorer</b></center>
<?
}
?>
There is nothing special about this form. It is a straight HTML form with no special tags of any kind. When the user fills in this form and hits the submit button, the action.php3 page is called. In this file you would have something like this:
<form action="action.php3" method="POST">
Your name: <input type=text name=name>
You age: <input type=text name=age>
<input type=submit>
</form>
It should be obvious what this does. There is nothing more to it. The $name and $age variables are automatically set for you by PHP.
Hi <?php echo $name?>. You are <?php echo $age?> years old.