In this tutorial, you’ll learn about PHP Variables, Constants and Parameters.
Variables are containers which we use for storing information. PHP variables work a bit differently to other languages so I suggest you pay close attention here.
A variable starts with a dollar sign ($) which is then followed by the name of the variable. That is then followed by a = sign and the value is entered after that. After the value you need a semi-colon as usual. Let’s have an example.
$variable_name = 100;
There are some important things you must remember when setting a variable name:
- The name of a variable must start with a letter or an underscore.
- Variable names are case sensitive (so $people would not be the same as $PEOPLE).
- A variable name cannot start with a number.
- A variable name can contain only letters, numbers and underscores.
When defining a variable you do not have to tell PHP the data type. This is where it is a bit different to other languages and shares more in common with something like python as PHP looks at what you set the variable too and gives it a datatype based on that.
Because of this, you also never need to declare a variable, it is created the moment you assign a value to it.
You can also use variables in other functions or constructs instead of directly typing in data. This comes in handy when you will be using a value more than once and don’t want to have to retype it and/or when the value of it will be changing often. For example:
$name = “Yeah Hub”;
//Since I put in the quotation marks PHP knows that is a string.
//Now the echo construct goes and looks for variable $name and outputs it.
A constant is similar to a variable except it is defined once then cannot be undefined or have its value changed. The same rules for making a constant variable name apply here.
To create a constant you use the define() function.
define(name, value, case-insensitive)
- name: Specifies the name of the constant.
- value: Specifies the value of the constant.
- case-insensitive: Should the constant name be case sensitive? This is defaulted to false.
define(“HELLO”, “Hello there friend.”);
//Outputs “Hello there friend.”
Example using case sensitive:
define(“HELLO”, “Hello my friend.”, true);
//Outputs “Hello my friend.”
You can also define constants by using the const variable. This works in exactly the same way but is always case-sensitive and is defined a little differently.
const CONSTANT = value;
Instead of using define, you simple remove the $ from in front of a variable and use the keyword const in front of the variable name.
Continue to Next Chapter – Complete PHP Tutorial – Chapter 4