PHP is an acronym for PHP Hypertext Processor. PHP files can contain HTML, CSS, and Javascript, which are run on a web server and sent to the browser as HTML.

PHP files end in the .php file extension.

What is PHP?

• PHP is an acronym for "PHP: Hypertext Preprocessor"
• PHP is a widely-used, open source scripting language
• PHP scripts are executed on the server
• PHP is free to download and use

A PHP script can be placed anywhere in the document.

A PHP script starts with <?php and ends with ?>

A simple PHP script

A variable starts with the $ followed by the name of the variable

Example

Rules for PHP Variables:

• A variable starts with the $ sign, followed by the name of the variable
• A variable name must start with a letter or the underscore character
• A variable name cannot start with a number
• A variable name can only contain alpha-numeric characters and underscores (A-z, 0-9, and _ )
• Variable names are case-sensitive ($age and $AGE are two different variables)

In PHP we have the following conditional statements.

• if statement - executes some code if one condition is true
• if...else statement - executes some code if a condition is true and another code if that condition is false
• if...elseif...else statement - executes different codes for more than two conditions
• switch statement - selects one of many blocks of code to be executed

In PHP we have the following loop types

• while - loops through a block of code as long as the specified condition is true
• do...while - loops through a block of code once, and then repeats the loop as long as the specified condition is true
• for - loops through a block of code a specified number of times
• foreach - loops through a block of code for each element in an array