Question

How to invert the bits of a number in PHP

Answer 1

function print_bits($n, $len = 8) {
    return str_pad(decbin($n), $len, "0", STR_PAD_LEFT);
}
 
$x = 981;
         
echo print_bits($x, 32) . "\n";
 
$x = ~$x;
 
echo print_bits($x, 32) . "\n";
 
 
 
  
/*
run:
   
00000000000000000000001111010101
1111111111111111111111111111111111111111111111111111110000101010
 
*/

 

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Answer 2

function print_bits($n, $len = 8) {
    return str_pad(decbin($n), $len, "0", STR_PAD_LEFT);
}

$x = 981;
        
echo print_bits($x, 32) . "\n";

$x = $x ^ 0xFFFFFFFF;

echo print_bits($x, 32) . "\n";



 
/*
run:
  
00000000000000000000001111010101
11111111111111111111110000101010

*/

 

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