Array Key Coercion

Cast passed value into a PHP "array key" type. An "array key" in PHP it can be one of two types, either a string or an int number.

Input Value	Output Result	Description
`string(T)`	`string(T)`	Returns string value "as is"
`int(T)`	`int(T)`	Returns int value "as is"
`bool(false)`	`int(0)`
`bool(true)`	`int(1)`
`null`	`int(0)`
`float(T)`	`int(T)`	Converts float to an int without losing precision ^[1]
`Stringable`	`string(T)`	Converts `Stringable` object to a string ^[2]
`BackedEnum`	`string(BackedEnum::$value)`	Returns the value of the backed enum's case
`UnitEnum`	`string(UnitEnum::$name)`	Returns the name of the unit enum's case
Other	`never`	Throws `InvalidValueException` exception

The float value must satisfy the following rules:
- Must not be more than PHP_INT_MAX
- Must not be less than PHP_INT_MIN
- The mantissa should be 0 (should be no loss of precision)
For objects implementing the Stringable interface, the __toString() method will be called.

05 November 2025