PHP Program to Reverse Bit of a Number

Given a number N, the task is to Reverse the Bit of the number and convert back into a decimal number in PHP.

Examples:

Input: N = 11
Output: 13
Explanations: (11)10 = (1011)2 
                         After revering the Bits (1101)2 = (13)10

Approach 1: Reverse Bit of a Number using Bitwise Shift Operators

In this approach, we obtain each bit of the binary representation of the number N by using the bitwise right shift operator. We then accumulate these bits in the variable "rev" using the bitwise left shift operation.

PHP

<?php

function reverseBits($number) {
    $reverse = 0;
     
    while ($number > 0) {
        // Bitwise left shift 'rev' by 1
        $reverse <<= 1;
         
        // If current bit is '1'
        if ($number & 1 == 1)
            $reverse ^= 1;
         
        // Bitwise right shift 'n' by 1
        $number >>= 1;
    }
     
    // Required number
    return $reverse;
}

// Driver Code
$number = 11;
$reversedNumber = reverseBits($number);
echo "Reversed Number: $reversedNumber";

?>

Output

Reversed Number: 13

Approach 2: Reverse Bit of a Number using PHP Functions

The PHP function reverseBits($number) takes an integer as input, converts it to its binary representation, reverses the binary string, and then converts it back to an integer.

• Convert the input number to its binary representation using decbin($number). This gives us a binary string.
• Convert the binary string to a regular string using strval($binary).
• Reverse the string using strrev($binString) to get the reversed binary string.
• Convert the reversed binary string back to an integer using bindec($revBin).

PHP

<?php

function reverseBits($number) {
    
    $binary = decbin($number);
    echo $binary . "\n";
    
    $binString = strval($binary);
    $revBin = strrev($binString);
    $revNum = bindec($revBin);
    
    // Required number
    return $revNum;
}

// Driver Code
$number = 11;
$reversedNumber = reverseBits($number);
echo "Reversed Number: $reversedNumber";

?>

Output

1011
Reversed Number: 13