Bonnes Pratiques Web & Cloud

PHP does not require (or support) explicit type definition in variable declaration; a variable's type is determined by the context in which the variable is used. That is to say, if a string value is assigned to variable $var, $var becomes a string. If an integer value is then assigned to $var, it becomes an integer.

An example of PHP's automatic type conversion is the addition operator '+'. If either operand is a float, then both operands are evaluated as floats, and the result will be a float. Otherwise, the operands will be interpreted as integers, and the result will also be an integer. Note that this does not change the types of the operands themselves; the only change is in how the operands are evaluated and what the type of the expression itself is.

The following tables demonstrate behaviors of PHP types and comparison operators, for both loose and strict comparisons. This supplemental is also related to the manual section on type juggling.

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 (aka callable)
• array|object
• void

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.