The Bitwise right shift assignment operator (>>=) assigns the first operand a value equal to the result of Bitwise right shift operation of two operands.

(x >>= y) is equivalent to (x = x >> y)

The Bitwise right shift operator (>>) takes the two numbers and right shift the bits of first operand by number of place specified by second operand. For example: for right shifting the bits of x by y places, the expression (x>>y) can be used. It is equivalent to dividing x by 2y.

The below example describes how right shift operator works:

```1000 >> 2 returns 250

(In Binary)
1000         ->    1111101000
>> 2                     |  right shift the bits
-----                    V  by 2 places
250         <-      11111010
(In Binary)
```

The code of using right shift operator (>>) is given below:

```<?php
\$x = 1000;

//right shift assignment operation
\$x >>= 2;

//Displaying the result
echo "x = \$x";
?>
```

The output of the above code will be:

```x = 250
```

### Example: Find largest power of 2 less than or equal to given number

Consider an integer 1000. In the bit-wise format, it can be written as 1111101000. However, all bits are not written here. A complete representation will be 32 bit representation as given below:

```00000000000000000000001111101000
```

Performing N = N | (N>>i) operation, where i = 1, 2, 4, 8, 16 will change all right side bit to 1. When applied on 1000, the result in 32 bit representation is given below:

```00000000000000000000001111111111
```

Adding one to this result and then right shifting the result by one place will give largest power of 2 less than or equal to 1000.

```00000000000000000000001000000000
```

The below code will calculate the largest power of 2 less than or equal to given number.

```<?php
function MaxPowerOfTwo(\$N) {
//changing all right side bits to 1.
\$N = \$N | (\$N>>1);
\$N = \$N | (\$N>>2);
\$N = \$N | (\$N>>4);
\$N = \$N | (\$N>>8);
\$N = \$N | (\$N>>16);

//adding 1 to \$N makes smallest power
//of 2 greater than given number
\$N = \$N + 1;

//right shift by one position makes
//largest power of 2 less than or
//equal to given number
\$N >>= 1;
return \$N;
}

echo "MaxPowerOfTwo(100) = ".
MaxPowerOfTwo(100)."\n";
echo "MaxPowerOfTwo(500) = ".
MaxPowerOfTwo(500)."\n";
echo "MaxPowerOfTwo(1000) = ".
MaxPowerOfTwo(1000)."\n";
?>
```

The above code will give the following output:

```MaxPowerOfTwo(100) = 64
MaxPowerOfTwo(500) = 256
MaxPowerOfTwo(1000) = 512
```

❮ PHP - Operators