What is the PHP7 new scalar type and return type declaration performance?

What is the PHP7 new scalar type and return type declaration performance?

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Performance improvements are not, instead introduce a strict type check, in the normal case will increase the runtime overhead.
This feature is not intended for performance reasons.

Of course, type hinting helps with type inference, and PHP 7.1 has added a "like" JIT technique (type specifical opcode handler), such as if the type infers that $ A is int and $b is int, then $a + $b can use Zend_add_long handler, thereby indirectly improving performance.

But, in general, the initial starting point for this feature is not performance.

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