A brief analysis of the differences and efficiency between i++ and ++i in PHP

This article mainly introduces relevant information about 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

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 1 to i

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

Watch some video tutorials and write i instead of i when writing a for loop. Go online. After searching, it turns out that there is an 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 out these differences, then the efficiency will be almost the same.

Let me explain in detail the difference between i and i

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

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

Finally The value of a is equal to 3 and the value of i 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 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 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 adds 1 to the i value, and i first assigns i to the new variable.

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