为什么$ a + = 3的执行速度比$ a = $ a + 3快？

Question

PHP manual states that:

Adding 3 to the current value of $a can be written '$a += 3'. This means exactly "take the value of $a, add 3 to it, and assign it back into $a". In addition to being shorter and clearer, this also results in faster execution.

I used to think that $a += 3 is merely syntax sugar for $a = $a + 3 and thus they should be equal in all respects.

Why does $a += 3 result in faster execution compared to $a = $a + 3?

Answer 1

$a = $a + 3 adds 3 to $a in a temporary memory space, then assigns the result to $a; while $a += 3 adds 3 directly to $a; so the difference is a few bytes of memory for temporary storage, plus an assignment