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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).

  • 0:00

    [MUSIC]

  • 0:04

    [SOUND] There are two basic parts to writing code, the storage and retrieval of

  • 0:09

    data, and the logic that tells what and when to do something with that data.

  • 0:14

    There are many, many ways to handle these two pieces, and that's one of the things I

  • 0:19

    enjoy about programming, figuring out the best way to solve a problem.

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    We'll use both these pieces to create a simple program for

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    converting units of measurement.

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    Variables are the most basic way of storing and

  • 0:32

    keeping track of information in a program.

  • 0:35

    For example, a computer game keeps track of a player's score.

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    At the start of the game, the score is zero.

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    It can go up if the player does well, or go down if the player makes a mistake.

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    The game might even end if the player reaches a particular score.

  • 0:51

    Score is an example of a variable.

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    Although the score's value will change, 0 at the beginning, 100 at the end for

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    example, it's still always just one score for that player.

  • 1:03

    Think of a variable as a box.

  • 1:05

    You can put something inside the box, look inside the box to see what's inside it,

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    empty the box, and even put something new inside the box.

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    While the contents of the box changes, it's still always the same box.

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    A program might need lots of variables, or

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    boxes, to keep track of lots of information.

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    In order for our program to follow all those variables,

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    we need a way to identify each variable in a program.

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    That's why each variable has its own name, like score,

  • 1:36

    which identifies that one variable.

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    Variables in PHP always begin with a dollar sign,

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    followed immediately by an underscore or a letter, and

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    then any combination of numbers letters and underscores.

  • 1:51

    You cannot start a variable with a number.

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    We could call this variable $score.

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    Our variable score represents the box.

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    When you create a variable you can leave it empty.

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    In that case, add a semicolon to the end of a statement.

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    Or you can create the variable and put something into it in a single statement.

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    Using the equal sign, you can insert a value into a variable.

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    $score=0.

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    The single equal sign tells PHP to put whatever's on the right side into the name

  • 2:26

    on the left side.

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    In this example put zero into score.

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    When we place something in a variable we call that assigning a value

  • 2:35

    to the variable.

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    Throughout this course we'll be covering the four scalar, or base variable types

  • 2:42

    that are supported in PHP, boolean, integer, float and string.

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    A boolean value is either true or false.

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    You'll use these a lot when adding logic to your programs.

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    Integers are whole numbers such as 1 through 9 or -1 through -9.

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    A float is a number that uses a decimal place such as storing

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    the price of an item as 2.25.

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    A string variable combines any number of characters such as a sentence or

  • 3:14

    paragraph.

  • 3:16

    For example, Hello World!

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    PHP also supports two compound variable types that we'll look at in later courses,

  • 3:25

    array and object.

  • 3:27

    These types allow you to collect many different values into a single variable.

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    You'll be using variables often.

  • 3:34

    So let's get started exploring how to set, retrieve, and manipulate number variables.

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