PHP types

Introduction

PHP supports eight primitive types.

Four scalar types:

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boolean
integer
float (floating-point number, aka double)
string

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Two compound types:

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array
object

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And finally three special types:

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resource
NULL
callable

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

mixed
number
callback
And the pseudo-variable $....

Some references to the type "double" may remain in the manual. Consider double the same as float; the two names exist only for historic reasons.

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