Analyze the difference between i++ and ++i in PHP

This article mainly introduces relevant information that briefly analyzes the difference and efficiency between i++ and ++i in PHP. It is very good and has reference value. Friends in need can refer to it. I hope to be helpful.

Let’s look at the basic differences first:

i++: First use the current value of i in the expression where i is located, and then add i 1

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

Watch some video tutorials When writing a for loop, always write ++i instead of i++. After searching on the Internet, it turns out that there is an efficiency issue

++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 out these differences, then the efficiency will be almost the same.

Let me tell you the difference between ++i and i++ in detail

1. The usage of ++i (with a =++i, i=2 for example)

First add 1 to the i value (that is, i=i+1), and then assign it to 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, 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, ++i and i++ are equivalent to i=i+ when used alone 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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