The most worrisome breaking changes in PHP 8

 

Strict typing on internals in PHP 8

One of the most important breaking changes in PHP 8 has to do with strict typing. User-defined functions in PHP already throw a TypeError. However, internal functions emitted warnings and returned null. PHP 8 makes this consistent and internal functions now also throw a TypeError. This will not only impact functions that already threw warnings prior to PHP 8, but also magic methods (which previously weren’t type checked) and functions that have had type declarations introduced. For this reason, it’s not possible to catch all issues that arise from this change by fixing the type warnings in PHP 7.4 environments. Below is an overview of related breaking changes that together define the scope of strict typing related changes in PHP 8.

Consistent type errors

As of PHP 8 internal functions now throw a TypeError for all typed arguments.

Arithmetic operator type checks

The arithmetic and bitwise operators +, -, *, /, **, %, <<, >>, &, |, ^, ~, ++, — will now consistently throw a TypeError when one of the operands is an array, resource or non-overloaded object. The only exception to this is the array + array union operation, which remains supported.

Before PHP 8, it was possible to apply arithmetic or bitwise operators on arrays, resources or objects. This isn’t possible anymore, and will throw a TypeError.

Magic methods type checks

Magic Methods will now have their arguments and return types checked if they have them declared. The signatures should match the following list:

• __call(string $name, array $arguments): mixed
• __callStatic(string $name, array $arguments): mixed
• __clone(): void
• __debugInfo(): ?array
• __get(string $name): mixed
• __invoke(mixed $arguments): mixed
• __isset(string $name): bool
• __serialize(): array
• __set(string $name, mixed $value): void
• __set_state(array $properties): object
• __sleep(): array
• __unserialize(array $data): void
• __unset(string $name): void
• __wakeup(): void