PHP basics
PHP code can be declared in various places and can be used to print text as well as contain HTML tags.
This lesson focuses on:
- Declaring a script within a webpage
- Declaring a script in an external file
- Printing text on a webpage
- Including HTML tags in a script
- Including comments in a script
Declaring a script within a webpage
A PHP script begins with <?php and ends with ?>. It can be placed anywhere within a webpage. You can have as many scripts within a webpage as you want.
Syntax:
<?php script contents go here ?>
Example:
<html>
<head>
<title>PHP script</title>
</head>
<body>
<?php
print "PHP is cool!";
?>
</body>
</html>
Output of this example:
NOTE: Each line of code in PHP must end with a semicolon. The semicolon distinguishes one set of instructions from another. If you do not end a line of code in PHP with a semicolon, you will get an error!
Declaring a script in an external file
An external file in which a PHP script is declared should have a .php extension. This file will be included within the PHP source code of a webpage using the include() function inside an internal PHP script as if it is actually on the same webpage with the source code. The advantage to using external scripts is that you can include the same script(s) on several pages without having to rewrite them.
Example:
<html>
<head>
<title>External scripts</title>
</head>
<body>
<?php
include("script1.php");
?>
</body>
</html>
In this example, an internal script calls the external script named script1.php
NOTE: External scripts cannot contain the <?php ?> block. Only internal scripts can!
Printing text on a webpage
You can print text on a webpage in PHP using the print or echo commands.
Example:
<html>
<head>
<title>Print and echo commands</title>
</head>
<body>
<?php
print "Here is some text. ";
echo "Here is some more text.";
?>
</body>
</html>
Output:
Including HTML tags in a script
HTML tags can be included in a script using the print or echo commands mentioned above. Any tags included in a script through these commands will be interpreted by the web browser as regular HTML.
Example:
<html>
<head>
<title>HTML tags in scripts</title>
</head>
<body>
<?php
print "<b><i>This text will be bold and italic</i></b>";
echo "<br /><a href='http://www.landofcode.com'>
Landofcode.com main page
</a>";
?>
</body>
</html>
Output:
Landofcode.com main page
Including comments in a script
Comments in PHP are declared so that code would be easier to understand and to navigate. Comments are not seen on a webpage, but only within the source code. Comments can be placed anywhere within PHP source code. In PHP you can have single line comments and multi line comments.
Single line comments
Single line comments in PHP are declared with two / symbols.
Example:
<html>
<head>
<title>Single line comments</title>
</head>
<body>
<?php
//this is a single line comment
//this is another single line comment
?>
</body>
</html>
NOTE: Single line comments can span only a single line.
Multi line comments
Multi line comments in PHP are declared with a starting /* and an ending */
Example:
<html>
<head>
<title>Multi line comments</title>
</head>
<body>
<?php
/*
here is a multi line comment
it will span multiple lines
this is the third line of the multi line comment
*/
?>
</body>
</html>
NOTE: Multi line comments can span as many lines as you want.
