If the exact type of the value is not part of the union, then the target type is chosen in the following order of preference: int float string bool // type: *int|string* 42.0 → 42 // *float* compatible with *int* 42.1 → 42 // *float* compatible with int *(deprecated in PHP 8.1)* 1e100 → "1.0E+100" // *float* too large for *int* type, fall back to *string* INF → "INF" // *float* too large for *int* type, fall back to *string* true → 1 // *bool* compatible with *int* new ObjectWithToString → "Result of __toString()" // *object* never compatible with *int*, fall back to *string* [] → *TypeError* // *array* *not* compatible with *int* or *string*