PHP: decbin - Manual

decbin

Xavier Daull
04-Feb-2006 02:57


A fast function to convert a binary string to a bit sequence



<?php



function BinString2BitSequence($mystring) {    

    $mybitseq = "";

    $end = strlen($mystring);

    for($i = 0 ; $i < $end; $i++){

        $mybyte = decbin(ord($mystring[$i])); // convert char to bit string

        $mybitseq .= substr("00000000",0,8 - strlen($mybyte)) . $mybyte; // 8 bit packed

    }

    return $mybitseq;

}



echo BinString2BitSequence("ABCDEF"); // OUTPUT=010000010100001001000011010001000100010101000110



?>

06-Jan-2006 06:29


Just an example:

If you convert 26 to bin you'll get 11010, which is 5 chars long. If you need the full 8-bit value use this:



$bin = decbin(26);

$bin = substr("00000000",0,8 - strlen($bin)) . $bin;



This will convert 11010 to 00011010.

j dot preece at gmail dot com
03-Jan-2006 05:00


It occured to me there must be a simple way to produce binary numbers from decimal ones with any number of bits, here's my attempt at a decimal to extended binary function. I hope the comments make it clear:



<?php



function decextbin($decimalnumber,$bit)

{

    /* decextbin function

            by James Preece (j.preece@gmail.com)

            http://www.lovingit.co.uk

    

    Please feel free to use this function. If you find

    if useful I would love to hear from you.

    */



    /* Function to return a binary number with as many

    bits as are requested...

    

    This works on the following principal. A binary number

    represents a figure 2,4,8,16 etc. If we work from the

    top down we can determine if a number contains each figure

    as a fraction and then work with what remains.

    

    For example, if we wish to display the number 10 as a 4 bit

    number we first discover the figure of the maximum bit by doubling

    four times:



    1 2 4 8

    

    The maxiumum figure is 8. 

    

    Next we work down the figures:

    

    8 goes in to 10 so the first digit is 1 leaving 2

    4 does not go in to 2 so the second digit is 0

    2 goes in to 2 so the third digit is 1

    1 does not go in to 0 so the fourth digit is 0

    

    Output: 1010

    

    Now for the actual code!



    First we find that maximum value represented by the

    leftmost binary digit. For error checking purposes

    we also calulate the maximum number we can display

    using the number of bits requested:        */

    

    $maxval = 1;

    $sumval = 1;

    for($i=1;$i<$bit;$i++)

    {

        $maxval = $maxval * 2;

        $sumval = $sumval + $maxval;

    }

    

    /* Using our sumval we now check if it is possible

    to display the decimal number our function received: */

        

    if ($sumval < $decimalnumber) return 'ERROR - Not enough bits to display this figure in binary.';

    

    /* Then we work down through the figures, to get a

    better idea of how this works remove the commenting

    from the echo lines */

    

    for($bitvalue=$maxval;$bitvalue>=1;$bitvalue=$bitvalue/2)

    {

            //echo 'Bit Value: '.$bitvalue.'<br />';

            //echo 'Decimal Number: '.$decimalnumber.'<br />';

        

        if (($decimalnumber/$bitvalue) >= 1) $thisbit = 1; else $thisbit = 0;

        

            //echo 'This Bit: '.$thisbit.'<br /><br />';

    

        if ($thisbit == 1) $decimalnumber = $decimalnumber - $bitvalue;

    

    $binarynumber .= $thisbit;

    }



    /* Finally we return the output... */



return $binarynumber;

}



?>



An example usage might be like so:



<?php



for ($i = 0;$i<=8;$i++)

{

    echo decextbin($i,4).'<br />';

}



?>



Output:



0000

0001

0010

0011

0100

0101

0110

0111

1000



No need for padding or anything - also goes way over 32 bits. Huzzah. I suspect its limited by the maximum string length in php. Hmmm - Not sure what that is.

dcramer at gmail dot com
26-Apr-2005 04:57


matt at nexxmedia dot com (06-Dec-2002 04:29) said:

<?php

...

strrev(str_pad(decbin($decval),8,"0",STR_PAD_LEFT));

...

?>



<?php

str_pad(decbin ($decval),8,'0');

?>



produces the same results!

--

That's incorrect, it does not produce the same results.

Stefan
02-Mar-2005 11:35


matt at nexxmedia dot com (06-Dec-2002 04:29) said:

<?php

...

strrev(str_pad(decbin($decval),8,"0",STR_PAD_LEFT));

...

?>



<?php

str_pad(decbin ($decval),8,'0');

?>



produces the same results!

08-Feb-2005 07:27


base_convert( base_convert('100001000100000000010001001000

0100100000001111111111111111111',2,10),10,2);



return

'1000010001000000000100010010000

100100000010000000000000000000'



this function doesn't work

27-Nov-2004 07:26


<?php // function for converting values >= 2147483648 (2^16)

  function decbin4long($long) {

    return base_convert($long,10,2);

  } // idea from http://phpclub.ru/talk/showthread.php?postid=407488

?>

gene_wood at example dot com
15-Oct-2003 02:38


This is just an extension off of the first comment. This is a pair of function to convert from an array of binary values to an integer and vice versa. It has a touch of error checking.



/**

* Will convert an array of binary values into an integer for storage

*

* @param        array       $data_array     Array of 31 or less binary values 

* @return       integer                     Encoded integer

*/

function array_to_binary_int($data_array) {

    if (count($data_array) > 31) return FALSE;

    foreach ($data_array as $key => $value) {

        if ($value) $data_array[$key] = 1;

        if (!$value) $data_array[$key] = 0;

    }

    $binstring = strrev(implode('', $data_array));

    $bit_integer = bindec($binstring);

    return $bit_integer;

}



/**

* Will convert a stored integer into an array of binary values

*

* @param        integer       $data_integer     Encoded integer

* @return       integer                         Array of binary values

*/

function binary_int_to_array($data_integer) {

    if (($data_integer > 2147483647) OR ($data_integer < 0)) return FALSE;

    $binstring = strrev(str_pad(decbin ($data_integer),31,"0",STR_PAD_LEFT));

    $bitarray = explode(":",chunk_split($binstring, 1, ":"));

    return $bitarray;

}

matt at nexxmedia dot com
05-Dec-2002 06:29


A quick one-line bitmask. Great for storing a list of checkbox settings in a MySQL database. This one works for TinyINT (8 bits). Note: I had to make it two lines here so it would fit.



$decval = 83;



/*

decimal to binary, padded with 0s, reversed so the least significant digit is first, split with colons, and then separated into an array

*/



$binstring = strrev(str_pad(decbin ($decval),8,"0",STR_PAD_LEFT))

$bitarray = explode(":",chunk_split($binstring, 1, ":"));



for($x = 0; $x < 8; $x++) {

 echo $bitarray[$x]." ";

}



// will output 1 1 0 0 1 0 1 0

php at silisoftware dot com
28-Feb-2002 07:15


Another larger-than-31-bit function.

Works for very large numbers, but at the expense of perfect bit-precision as the size increases (I noticed rounding errors past 16 or so decimal places) so use with caution, and only when decbin() won't cut it.



function Dec2Bin($number) {

    while ($number >= 256) {

        $bytes[] = (($number / 256) - (floor($number / 256))) * 256;

        $number = floor($number / 256);

    }

    $bytes[] = $number;

    for ($i=0;$i<count($bytes);$i++) {

        $binstring = (($i == count($bytes) - 1) ? decbin($bytes[$i]) : str_pad(decbin($bytes[$i]), 8, "0", STR_PAD_LEFT)).$binstring;

    }

    return $binstring;

}

gthompsn at ucar dot edu
22-Jan-2002 11:04


To pad leading zeroes onto the output of decbin, I prefer to use something like this for my 8-bit integer:

 $qcStr=sprintf("%08d",decbin($myInt));



--Greg T.

ajl at gmx dot de
08-Oct-2001 01:47


HERE you can convert 64bit instead of 32bit with the standard decbin


<?


function bigdecbin($dec,$doublewords=1) {


    $erg = "";


    do {


          $rest = $dec%2147483648;


          if ($rest<0) $rest+=2147483648;


          $erg = str_pad(decbin($rest),31,"0",STR_PAD_LEFT).$erg;


          $dec = ($dec-$rest)/2147483648;


      } while (($dec>0)&&(!($dec<1)));


      


      return str_pad($erg,$doublewords*31,"0",STR_PAD_LEFT);


}





echo "<pre>";


for ($i=1.5*2147483647.0-10;$i<1.5*2147483647.0+10;$i++) {


    echo "DEC:".$i." BIN:".bigdecbin($i,2)."<br>";


}


echo "</pre>";


?>

sam at barnum dot com
12-Apr-2001 07:26


or pad the string like:


   substr("000" . $decbin($i), -3, 3);

nospam dot me at padamj dot com
11-Mar-2001 05:56


do this to pad the binary:





str_pad(decbin($dec),3,"0",STR_PAD_LEFT);





output like:


001


010

oubiwann at yahoo dot com
17-Jan-2001 04:04


Here's a little binary for counting on your fingers up to 1023 (from 0). It formats/pads the binary number like you wanted.


<pre>


&lt;?php


print "<pre>Dec  : Finger Positions\n";


print "---- : ----------------\n";


for ( $i=0; strlen($bin) <=10; ++$i ) {


   $bin = decbin($i);


   $output = sprintf("%04d : ", $i);


   $bin_temp = $bin;


   while ( strlen($bin_temp) < 10 ) {


      $bin_temp = "0" . $bin_temp;


   }


   print $output . $bin_temp . "\n";


}


print "</pre>\n";


?>


</pre>





I tried using sprintf("%04d : %10d", $i, $bin) and sprintf("%04d : %10d", $i, $bin + 0), the later an attempt to force the string to act as a number, but neither worked. Maybe it was me...

sterba at locksley-west dot com
10-Jan-2001 12:55


I had the same problem on PHP 3.0.9, so the str_repeat was not an option. This maight help:





while (strlen($result)<3) $result="0".$result;

decbin

Description