PHP Constants | Tutorial

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Tutorial Content:

A constant is an identifier for a given value. A constant cannot be changed during the script, as a variable can.

Also, unlike variables a constant is automatically global across the entire script.

When creating a constant, the name must start with a letter or underscore. A constant does not require a $ sign before the name.

As shown in this example, a constant can be created using the define() function.

Inside the function, we start with the constant name, followed by the value. We can also specify if the constant name should be case-insensitive. We will do that in the second example.

In this example, the constant name is WELCOME, the value is the text "hello my name is John Smith", the constant name is case-sensitive.

We can output the constant by creating an echo statement followed by the constant name, WELCOME.

If we were to set the echo statement to lowercase welcome, the output would not work.

In this second example, we have set the case-insensitive value to true.

This means, when we output our constant (welcome2) it doesn't matter if we use uppercase or lowercase for the constant name.

Constants are global and can be used across the entire script.

In this example, we have defined the constant car, and set the value to Volvo.

We have also created a function (mycar) that outputs the value of constant car using an echo statement.

When we run the function, we can see the browser outputs the value VOLVO.