Converting a decimal number to binary in PHP

Question

I have this function which converts numbers from decimal to binary.

<?php
function DecimalTOBinary($num)
{
    $a = "";
    $b = "";
    $x = 0;
    while ($num !=0)
    {
        $b .= $num % 2;
        $num = $num /2;
    }
    /*
    for($i = strlen($b) -1;$i >=0;$i--)
    {
        a .= substr($b,$i,$i +1);
    }*/
    return $b;

}
?>

My problem is that it will return the string:

010010100000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000

I wish to return only:

How can I achieve this?

hakre · Accepted Answer · 2011-07-03 17:24:03Z

5

$num = $num / 2; probably does fractional division (implicitly converting to float), causing $num to approach 0 but taking a very long time to get there. Make it $num = floor($num / 2); to round it back down to an integer.

Note that there's also decbin(), the built-in method for achieving this.

Exemplary (but superfluous):

function DecimalTOBinary($num)
{
    return decbin($num);
}

edited Jul 3, 2011 at 17:24

hakre

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answered Jul 3, 2011 at 17:05

Core Xii

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Comments

Gabi Purcaru · Accepted Answer · 2011-07-03 17:09:18Z

2

If you want that function for practical reasons, do what @Core Xii says. If you want to implement that function to learn, you should use the floor function: $num = floor($num/2), because PHP thinks that $num is a float and doesn't divide it as an integer.

Also, you'll want to return strrev($b), because your digits will be reversed.

answered Jul 3, 2011 at 17:09

Gabi Purcaru

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Comments

Edoardo Pirovano · Accepted Answer · 2011-07-03 17:16:46Z

0

This function will do what you want:

<?php
function DecimalToBinary($num) {
    $i = "";
    while (floor($num) > 0) {
        $i .= $num % 2;
        $num /= 2;
    }
    return strrev($i);
}

The main changes are:

Flooring the number in while loop check
Reversing digits.
Removed unnecessary variables.

answered Jul 3, 2011 at 17:16

Edoardo Pirovano

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Comments

Mohsin Abbas · Accepted Answer · 2022-06-27 13:37:33Z

0

Try this code this solution done with recursive function:

 function getBinary($num) {
 $remainder = '';
 $remainder = $num % 2;
 $num = floor($num / 2);  
 if ($num>=1)
  {
    $remainder .= getBinary($num);
  }
  
 return $remainder;
} 
echo getBinary(10);

answered Jun 27, 2022 at 13:37

Mohsin Abbas

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Rohit Gupta Over a year ago

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