Differences and efficiency between I ++ and I in PHP _ php instance

This article mainly introduces the differences and efficiency of I ++ and ++ in PHP. it is very helpful for reference. if you need it, you can refer to it. Let's take a look at the basic differences:

I ++: first use the current value of I in the expression where I is located, and then add 1 to the expression

++ I: Let I add 1 first, and then use the new value of I in the expression where I is located.

When I read some video tutorials and wrote for loops, I wrote ++ I instead of I ++. I searched the internet and found the efficiency problem.

++ I is equivalent to the following code:

i += 1; return i; 

I ++ is equivalent to the following code:

j = i; i += 1; return j;

Of course, if the compiler will optimize these differences, the efficiency will be almost the same.

Let's explain in detail the differences between ++ I and I ++.

1. usage of ++ I (using a = ++ I, I = 2 as an example)

Add the I value to 1 (that is, I = I + 1) and then assign it to variable a (that is, a = I ),

The final a value is 3, and the I value is 3.

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

2. I ++ usage (take a = I ++, I = 2 as an example)

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

Then, the final a value is 2, and the I value is 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 independently, they are equivalent to I = I + 1.

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

The above section describes the differences and efficiency between I ++ and I in PHP. I hope to help you, if you have any questions, please leave a message and the editor will reply to you in time. I would like to thank you for your support for the script home website!