PHP Exercises: Check if the bits of the two given positions of a number are same or not

Last update on April 19 2025 11:50:42 (UTC/GMT +8 hours)

34. Check Bits at Positions

Write a PHP program to check if the bits of the two given positions of a number are same or not.

112 - > 01110000
Test 2nd and 3rd position
Result: True
Test 4th and 5th position
Result: False

Sample Solution:

PHP Code:

<?php
// Function to test if bits at two specified positions are equal
function test_bit_position($num, $pos1, $pos2) {
    // Adjust positions to start from 0 (as arrays in PHP are 0-indexed)
    $pos1--;
    $pos2--;
    
    // Convert the decimal number to a binary string and reverse it
    $bin_num = strrev(decbin($num));

    // Check if the bits at the specified positions are equal
    if ($bin_num[$pos1] == $bin_num[$pos2]) {
        return "true";
    } else {
        return "false";
    }
}

// Test case
echo test_bit_position(112, 5, 6) . "\n";

?>

Explanation:

Function Definition:

The test_bit_position($num, $pos1, $pos2) function checks if the bits at two specified positions in a number's binary representation are equal.

Adjust Bit Positions:

$pos1-- and $pos2-- adjust the positions to be zero-indexed, as PHP strings are zero-indexed (e.g., position 1 becomes 0).

Convert Number to Binary:

decbin($num) converts the decimal number $num to a binary string.
strrev() reverses the binary string to match the bit positions from right to left, making it easier to access bits by index.

Check Equality of Specified Bits:

The function checks if the bits at the adjusted positions $pos1 and $pos2 are equal:

If they are, it returns "true".
If not, it returns "false".

Test Case:

The function is tested with the number 112 and positions 5 and 6.
The result is printed with echo.

Output:

true

Flowchart:

For more Practice: Solve these Related Problems:

Write a PHP script to check if two specified bit positions in a number's binary representation are identical.
Write a PHP script to toggle the bits at given positions and then verify their new states.
Write a PHP script to compare bits at dynamic positions provided by user input and return a true/false result.
Write a PHP script to create a function that checks for bit symmetry between any two positions in a binary string.

PHP Code Editor:

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