The difference between ++i and i++ in php

1. The usage of ++i (take a=++i, i=2 as an example)

Add 1 to i (i=i+1), then assign a (a=i),

So a is equal to 3, and i is equal to 3.

So a=++i is the same thing as i=i+1, a=i

2. The usage of i++ (take a=i++, i=2 as an example)

Assign the i value to the variable a (a=i), then add the i value to 1 (i=i+1),

So a is equal to 2, and i is equal to 3.

So a=i++ is the same thing as a=i, i=i+1

3. ++i and i++

a=++i = i++, a=i

a=i++ is equivalent to a=i, i++

4. When used alone, ++i and i++ are equivalent to i=i+1

If a new variable is assigned, ++i first adds 1 to the i value, while i++ first assigns i to the new variable.