Learning PHP (1)
This article introduces PHP for the beginner.
Contents
Requirements
Learning and using PHP requires:
- A web server (or other computer) running the PHP interpreter.
- A text editor, to edit source code for PHP scripts.
- Text files with the .php file extension
- Knowledge of PHP
- Knowldge of HTML and CSS
Web server with PHP interpreter
Most web servers, including the widely-used Apache HTTP Server, have the PHP interpreter pre-installed.
Text editor
You can use any text editor to edit PHP files.
PHP files
PHP files have the .php extension.
PHP and HTML
PHP pages can contain HTML (and CSS, and JavaScript), which behaves the same as it does in static web pages.
PHP code
PHP code is text consisting of one or more statements in the PHP programming language.
The examples below will introduce simple PHP statements.
PHP page without PHP?
In principle, a PHP page could be all HTML, with no PHP code.
This is not typically done, as it would defeat the purpose of PHP.
PHP code islands
PHP code islands (or code blocks) contain PHP code.
PHP code islands must not include HTML, CSS or JavaScript; using these languages inside a code island will trigger a PHP error.
You can use PHP code to generate text, including HTML, CSS, etc. See Generating text (PHP).
Mixing code islands and HTML
You can freely mix HTML and code islands in a PHP page.
Code islands look like this:
<?php ?>
Where does the PHP code go?
Beginners commonly ask: Where does the PHP code island go in the page?
Answer:
- If the code island contains PHP code which generates text, put the code island where you want the text to appear in the page.
- If the code island does not generate content, the code island typically goes at the top of the page, although this is not a requirement.
All PHP
A PHP page can be all PHP: one code island, no static HTML.
This is common with web applications, such as WordPress.
Web template systems
Web applications commonly have a mix of:
- All-PHP pages
- Pages which mix HTML with code islands according to a web template system.
