Object Oriented Programming in PHP : Constants

A constant is somewhat like a variable, in that it holds a value, but is really more like a function because a constant is immutable. Once you declare a constant, it does not change.

Declaring one constant is easy, as is done in this version of MyClass:

class MyClass { const requiredMargin = 1.7; function __construct($incomingValue) { // Statements here run every time // an instance of the class // is created. } }

In this class, requiredMargin is a constant. It is declared with the keyword const, and under no circumstances can it be changed to anything other than 1.7. Note that the constant's name does not have a leading $, as variable names do.