Variables can store data of different types, and different data types can do different things.
PHP supports the following data types:
A string is a sequence of characters, like "Hello world!".
A string can be any text inside quotes. You can use single or double quotes:
An integer is a whole number (without decimals). It is a number between -2,147,483,648 and +2,147,483,647.
Rules for integers:
In the following example $x is an integer. The PHP var_dump() function returns the data type and value:
A float (floating point number) is a number with a decimal point or a number in exponential form.
In the following example $x is a float. The PHP var_dump() function returns the data type and value:
A Boolean represents two possible states: TRUE or FALSE.
Booleans are often used in conditional testing. You will learn more about conditional testing in a later chapter of this tutorial.
An array stores multiple values in one single variable.
In the following example $cars is an array. The PHP var_dump() function returns the data type and value:
You will learn a lot more about arrays in later chapters of this tutorial.
An object is a data type which stores data and information on how to process that data.
In PHP, an object must be explicitly declared.
First we must declare a class of object. For this, we use the class keyword. A class is a structure that can contain properties and methods:
You will learn more about objects in a later chapter of this tutorial.
Null is a special data type which can have only one value: NULL.
A variable of data type NULL is a variable that has no value assigned to it.
Tip: If a variable is created without a value, it is automatically assigned a value of NULL.
Variables can also be emptied by setting the value to NULL:
The special resource type is not an actual data type. It is the storing of a reference to functions and resources external to PHP.
A common example of using the resource data type is a database call.
We will not talk about the resource type here, since it is an advanced topic.