A brief analysis of the difference and efficiency between i and i in PHP_php example

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 i

i: Let i be incremented by 1 first, and then use the new value of i in the expression where i is located

After watching some video tutorials, when writing for loops, i is written instead of i. I searched online and found 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. 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, it is equivalent to i=i 1

If assigned to a new variable, i first increments the value of i by 1, and i first assigns i to the new variable.

The above is the entire description of the difference and efficiency between i and i in PHP introduced by the editor. I hope it will be helpful to you. If you have any questions, please leave me a message and the editor will reply to you in time. of. I would also like to thank you all for your support of the Script House website!