Step by Step solution about How to resolve the algorithm Bitwise operations step by step in the PHP programming language

Bitwise Operators in PHP

The provided PHP function, bitwise(), demonstrates the functionality of bitwise operators on integer values. Bitwise operators perform operations on individual bits of their operands, allowing for efficient manipulation of data at the bit level.

Function Arguments:

• $a: The first integer operand.
• $b: The second integer operand.

Helper Function: zerofill($a, $b)

Within the main function, there is a helper function called zerofill(). This function provides a logical right shift operation that preserves the sign bit (leftmost bit) of the integer:

• If $a is negative, it shifts the bits to the right while retaining the sign bit.
• If $b is 0, it shifts a 0 into the empty slot created by the shift (preserving the sign bit).
• Otherwise, it uses a bitwise operation to retain the sign bit while shifting.

Main Function Body:

Inside the bitwise() function, the following bitwise operations are performed and printed to the console:

1. $a & $b: Bitwise AND

• Calculates the bitwise AND of $a and $b.
• The result is an integer where each bit is 1 only if both corresponding bits in $a and $b are 1.

2. $a | $b: Bitwise OR

• Calculates the bitwise OR of $a and $b.
• The result is an integer where each bit is 1 if either corresponding bit in $a or $b is 1.

3. $a ^ $b: Bitwise XOR (Exclusive OR)

• Calculates the bitwise XOR of $a and $b.
• The result is an integer where each bit is 1 if the corresponding bits in $a and $b are different, and 0 otherwise.

4. ~ $a: Bitwise NOT (Negation)

• Calculates the bitwise negation of $a.
• The result is an integer where each bit is flipped (1s become 0s, and 0s become 1s).

5. $a << $b: Bitwise Left Shift

• Shifts the bits of $a left by $b positions.
• The result is an integer where the original bits are moved left, and the empty slots are filled with 0s.

6. $a >> $b: Bitwise Arithmetic Right Shift (Signed)

• Shifts the bits of $a right by $b positions, preserving the sign bit.
• The sign bit is extended into the empty slots created by the shift.

7. zerofill($a, $b): Logical Right Shift (Unsigned)

• Shifts the bits of $a right by $b positions, preserving the sign bit.
• A 0 is shifted into the empty slots, regardless of the sign bit. This operation is useful for handling positive integers without losing sign information.

function bitwise($a, $b)
{
    function zerofill($a,$b) { 
        if($a>=0) return $a>>$b;
        if($b==0) return (($a>>1)&0x7fffffff)*2+(($a>>$b)&1); // this line shifts a 0 into the sign bit for compatibility, replace with "if($b==0) return $a;" if you need $b=0 to mean that nothing happens
        return ((~$a)>>$b)^(0x7fffffff>>($b-1)); 

    echo '$a AND $b: ' . $a & $b . '\n';
    echo '$a OR $b: ' . $a | $b . '\n';
    echo '$a XOR $b: ' . $a ^ $b . '\n';
    echo 'NOT $a: ' . ~$a . '\n';
    echo '$a << $b: ' . $a << $b . '\n'; // left shift  
    echo '$a >> $b: ' . $a >> $b . '\n'; // arithmetic right shift
    echo 'zerofill($a, $b): ' . zerofill($a, $b) . '\n'; // logical right shift
}