What is right shift in php? how to use?

PHP is a popular server-side scripting language that can be used to build web applications and dynamic websites. In PHP, right shift is a basic bit operation that allows you to shift a number to the right by a specified number of bits, resulting in a new number. However, this operation has different meanings and uses in different situations. In this article, we will take a deep dive into the different uses of right shift in PHP and how to use it in coding.

1. What is right shift?

In computer programming, right shifting means moving a number to the right by a specified number of digits and filling the left vacancies with zeros. For example, if you want to shift the binary number 1010 to the right by 2 bits, the result is 0010, with the first two bits padded with zeros. In PHP, the right shift operation can be implemented with the >> operator, whose syntax is as follows:

$result = $num >> $shift;

where $num is the number to be moved, and $shift is the number of digits to be shifted. , $result is the result after shifting. For example, if you want to move the number 10 to the right by 2 places, you can use the following code:

$num = 10; 
$shift = 2; 
$result = $num >> $shift; 
echo $result; // 输出结果为 2

2. Use 1: Divide by the power of 2

To the right A common use of shifting in programming is to divide a number by a power of two. For example, if you want to divide a number by 4, you can move it two places to the right because 4 is equal to the power of 2. In addition, right shifting can be used to optimize division operations in computer programs, because on most computers, right shifting is much faster than division operations.

For example, suppose you want to calculate the square root of a number. You can use the following code:

$num = 16; 
$sqrt = sqrt($num); // 计算平方根 
echo $sqrt; // 输出结果为 4

However, this method requires calculating the square root of a number, which can be very computationally intensive. Instead, you can use the following code:

$num = 16; 
$result = $num >> 1; // 将数字除以 2，等价于 $num / 2 
$result = $result >> 1; // 将数字除以 4，等价于 $num / 4 
echo $result; // 输出结果为 4

As shown in the above code, first move $num to the right by one position, which is equivalent to dividing it by 2, and then move it to the right by one position, which is equivalent to dividing it by Divide by 4. This method is much faster than using the sqrt() function, and is generally faster than using the multiplication and division operators.

3. Use 2: Quickly calculate squares and cubes

Shifting to the right can also be used to quickly calculate squares and cubes. If you want to square a number, you shift it one place to the left, which is equivalent to multiplying it by 2 and then adding the result to itself. Likewise, if you want to cube a number, you can shift it two places to the left, which is equivalent to multiplying it by 4 and adding the square of the original number to the result. Here is a code example:

$num = 5; 
$square = ($num << 1) + $num; // 平方，等价于 $num * $num 
$cube = ($num << 2) + ($num << 1) + $num; // 立方，等价于 $num * $num * $num 
echo $square; // 输出结果为 25 
echo $cube; // 输出结果为 125

Using right shift can greatly simplify these calculations, because the right shift operation is the inverse operation of the left shift operation. For example, if you want to calculate the square of a number, you can use the following code:

$num = 5; 
$square = ($num >> 1) 
 $num * 4 - ($num >> 1) 
 ($num >> 1); 
echo $square; // 输出结果为 25

where $num >> 1 is equivalent to dividing $num by 2, and $num * 4 is equivalent The price is to move $num to the left two places, ($num >> 1) * ($num >> 1) to find the square of $num.

4. Summary

In PHP, right shift is a basic bit operation that can be used in many different scenarios, such as dividing by 2 Power, quickly calculate squares and cubes, etc. By using the right shift operation appropriately, you can optimize your computer program and make it faster and more efficient. Hopefully this article helped you better understand bit shifting operations in PHP and apply it in your coding.

The above is the detailed content of What is right shift in php? how to use?. For more information, please follow other related articles on the PHP Chinese website!