They are whole numbers, without a decimal point, like 4195. They are the simplest type and correspond to simple whole numbers, both positive and negative. Integers can be assigned to variables, or they can be used in expressions,
They like 3.14159 or 49.1. By default, doubles print with the minimum number of decimal places needed.
They have only two possible values either true or false. PHP provides a couple of constants especially for use as Booleans: TRUE and FALSE.
NULL is a special type that only has one value: NULL. To give a variable the NULL value, simply assign it like this – $var=NULL;
They are sequences of characters.
$str= “Hello World”;