Detailed explanation of the difference between ++i and i++ in php_PHP tutorial

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

First add 1 to the i value (that is, i=i+1), and then assign it to the variable a (that is, a=i),

　 Then the final a value is equal to 3 and the i value is equal to 3.

　So a=++i is equivalent to i=i+1, a=i

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

First assign the i value to the variable a (that is, a=i), then add 1 to the i value (that is, i=i+1),

　 Then the final a value is equal to 2 and the i value is equal to 3.

So a=i++ is equivalent to a=i , i=i+1

3. ++i and i++

　a=++i is equivalent to i++, a=i

　a=i++ is equivalent to a=i, i++

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

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

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