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Casting

Casts in Hack convert values to different types. To assert a type without changing its value, see type assertions.

(float)1; // 1.0
(int)3.14; // 3, rounds towards zero
(string)false; // ""

Casts are only supported for int, float and string.

Casting to int​

If the source type is bool, then if the source value is false, the result value is 0; otherwise, the result value is 1.

If the source type is float, for the values INF, -INF, and NAN, the result value is implementation-defined. For all other values, if the precision can be preserved, the fractional part is rounded towards zero and the result is well defined; otherwise, the result is undefined.

If the source value is null, the result value is 0.

If the source is a numeric string or leading-numeric string having integer format, if the precision can be preserved the result value is that string's integer value; otherwise, the result is undefined. If the source is a numeric string or leading-numeric string having floating-point format, the string's floating-point value is treated as described above for a conversion from float. The trailing non-numeric characters in leading-numeric strings are ignored. For any other string, the result value is 0.

If the source is an array with zero elements, the result value is 0; otherwise, the result value is 1.

If the source is a resource, the result is the resource's unique ID.

The library function intval allows values to be converted to int.

Casting to float​

If the source type is int, if the precision can be preserved the result value is the closest approximation to the source value; otherwise, the result is undefined.

If the source is a numeric string or leading-numeric string having integer format, the string's integer value is treated as described above for a conversion from int. If the source is a numeric string or leading-numeric string having floating-point format, the result value is the closest approximation to the string's floating-point value. The trailing non-numeric characters in leading-numeric strings are ignored. For any other string, the result value is 0.

If the source is an array with zero elements, the result value is 0.0; otherwise, the result value is 1.0.

If the source is a resource, the result is the resource's unique ID.

The library function floatval allows values to be converted to float.

Casting to string​

If the source type is bool, then if the source value is false, the result value is the empty string; otherwise, the result value is "1".

If the source type is int or float, then the result value is a string containing the textual representation of the source value (as specified by the library function sprintf).

If the source value is null, the result value is an empty string.

Objects cannot be cast to strings.

If the source is a resource, the result value is an implementation-defined string.

The library function strval allows values to be converted to string.