Introduction

PHP supports eight primitive types.

Four scalar types:

• boolean

• integer

• float (floating-point number, aka 'double')

• string

Two compound types:

• array

• object

And finally two special types:

• resource

• NULL

This manual also introduces some pseudo-types for readability reasons:

• mixed

• number

• callback

You may also find some references to the type "double". Consider double the same as float, the two names exist only for historic reasons.

The type of a variable is usually not set by the programmer; rather, it is decided at runtime by PHP depending on the context in which that variable is used.

If you would like to force a variable to be converted to a certain type, you may either cast the variable or use the settype() function on it.

Note that a variable may be evaluated with different values in certain situations, depending on what type it is at the time. For more information, see the section on Type Juggling. Also, you may be interested in viewing the type comparison tables, as they show examples of various type related comparisons.