Before you continue you should have a basic understanding of the following:
### HTML
### CSS
### JavaScript
PHP files can contain Text, HTML, CSS, JavaScript, and PHP code.
A PHP script is executed on the server, and the plain HTML result is sent back to the browser.
A PHP script starts with `<?php` and ends with `?>`:
```php
<?php
// PHP code goes here
?>
```
or
you can also write A PHP script starts with `<?php` and ends without `?>`:
```php
<?php
// PHP code goes here
```
Below, we have an example of a simple PHP file, with a PHP script that uses a built-in PHP function "echo" to output the text "Hello World!" on a web page:
Note: You cannot simply open this file with your browser as you could with an html file. In order for this file to display properly in your browser, you must place it in an accessible folder on a server. A simple example: To do this in apache, you would be replacing the "index.html" file with this file and naming it "index.php" (You should check that php is enabled on your apache server).
