Heads up! To view this whole video, sign in with your Courses account or enroll in your free 7-day trial. Sign In Enroll

Preview

Start a free Courses trial
to watch this video

Sign up for Treehouse

Variables in PHP

3:40 with Alena Holligan

Variables are the most basic way of storing and keeping track of information in a program. Throughout this course, we'll be covering the 4 scalar, or base variable types that are supported in PHP: boolean, integer, float and string.

Variables in PHP

The type of a variable is not usually set by the programmer; rather, it is decided at runtime by PHP depending on the context in which that variable is used. PHP supports eight primitive types.

  1. Four scalar types:
    • boolean
    • integer
    • float (floating-point number, aka double)
    • string
  2. Two compound types:
    • array
    • object
  3. And finally two special types:
    • resource
    • NULL

Why variables can't start with a number.

This is a standard for all programming languages. Primarily to standardize between languages whose variables do not start with a symbol. It is easier for a compiler to make an assumption that if a token begins with a number, it is most likely a numeric value rather than a variable name and any non-numeric characters that are a part of the token would assist in determining the numeric type or number system (12e5 is a valid number).

[MUSIC] 0:00
[SOUND] There are two basic parts to writing code, the storage and retrieval of 0:04
data, and the logic that tells what and when to do something with that data. 0:09
There are many, many ways to handle these two pieces, and that's one of the things I 0:14
enjoy about programming, figuring out the best way to solve a problem. 0:19
We'll use both these pieces to create a simple program for 0:24
converting units of measurement. 0:27
Variables are the most basic way of storing and 0:29
keeping track of information in a program. 0:32
For example, a computer game keeps track of a player's score. 0:35
At the start of the game, the score is zero. 0:39
It can go up if the player does well, or go down if the player makes a mistake. 0:42
The game might even end if the player reaches a particular score. 0:47
Score is an example of a variable. 0:51
Although the score's value will change, 0 at the beginning, 100 at the end for 0:54
example, it's still always just one score for that player. 0:58
Think of a variable as a box. 1:03
You can put something inside the box, look inside the box to see what's inside it, 1:05
empty the box, and even put something new inside the box. 1:10
While the contents of the box changes, it's still always the same box. 1:14
A program might need lots of variables, or 1:18
boxes, to keep track of lots of information. 1:22
In order for our program to follow all those variables, 1:25
we need a way to identify each variable in a program. 1:28
That's why each variable has its own name, like score, 1:32
which identifies that one variable. 1:36
Variables in PHP always begin with a dollar sign, 1:38
followed immediately by an underscore or a letter, and 1:42
then any combination of numbers letters and underscores. 1:46
You cannot start a variable with a number. 1:51
We could call this variable $score. 1:53
Our variable score represents the box. 1:57
When you create a variable you can leave it empty. 2:00
In that case, add a semicolon to the end of a statement. 2:04
Or you can create the variable and put something into it in a single statement. 2:07
Using the equal sign, you can insert a value into a variable. 2:13
$score=0. 2:18
The single equal sign tells PHP to put whatever's on the right side into the name 2:21
on the left side. 2:26
In this example put zero into score. 2:27
When we place something in a variable we call that assigning a value 2:31
to the variable. 2:35
Throughout this course we'll be covering the four scalar, or base variable types 2:37
that are supported in PHP, boolean, integer, float and string. 2:42
A boolean value is either true or false. 2:49
You'll use these a lot when adding logic to your programs. 2:52
Integers are whole numbers such as 1 through 9 or -1 through -9. 2:56
A float is a number that uses a decimal place such as storing 3:01
the price of an item as 2.25. 3:06
A string variable combines any number of characters such as a sentence or 3:09
paragraph. 3:14
For example, Hello World! 3:16
PHP also supports two compound variable types that we'll look at in later courses, 3:19
array and object. 3:25
These types allow you to collect many different values into a single variable. 3:27
You'll be using variables often. 3:32
So let's get started exploring how to set, retrieve, and manipulate number variables. 3:34

You need to sign up for Treehouse in order to download course files.

Sign up