PHP Unconference Europe 2015

decbin

(PHP 4, PHP 5)

decbinDa decimale a binario

Descrizione

string decbin ( int $numero )

Restituisce una stringa contenente una rappresentazione binaria di un dato argomento numero. Il più grande numero che può essere convertito è 4294967295 in decimale, risultante in una stringa composta da 32 volte la cifra 1.

Example #1 Esempio per decbin()

<?php 
echo decbin(12) . "\n"
echo 
decbin(26); 
?>

L'esempio precedente visualizzerà:

 
1100 
11010 

Vedere anche bindec(), decoct(), dechex() e base_convert().

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User Contributed Notes 13 notes

up
10
MarcelG
8 months ago
To add leading zeros I prefer the following:
<?php
// Add leading zeros
$bin = sprintf( "%08d", decbin( 26 )); // "00011010"
?>
up
8
Anonymous
8 years ago
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.
up
3
Xavier Daull
8 years ago
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

?>
up
2
Nitrogen
5 years ago
Decimal to Binary conversion using the BCMath extension.

<?php

function BCDec2Bin($Input='') {
$Output='';
if(
preg_match("/^\d+$/",$Input)) {
   while(
$Input!='0') {
    
$Output.=chr(48+($Input{strlen($Input)-1}%2));
    
$Input=BCDiv($Input,'2');
   }
  
$Output=strrev($Output);
}
return((
$Output!='')?$Output:'0');
}

?>

This will simply convert from Base-10 to Base-2 using BCMath (arbitrary precision calculation).

See also: my 'BCBin2Dec' function on the 'bindec' document.
Enjoy,
Nitrogen.
up
0
mcampa at gmail dot com
1 year ago
A little useful little function that returns a binary string with leading 0s:

function d2b($n) {
  return str_pad(decbin($n), 16, "0", STR_PAD_LEFT);
}

// example:
echo d2b(E_ALL);
echo d2b(E_ALL | E_STRICT);
echo d2b(0xAA55);
echo d2b(5);

Output:
0111011111111111
0111111111111111
1010101001010101
0000000000000101
up
0
Anonymous
9 years ago
base_convert( base_convert('100001000100000000010001001000
0100100000001111111111111111111',2,10),10,2);

return
'1000010001000000000100010010000
100100000010000000000000000000'

this function doesn't work
up
0
ajl at gmx dot de
13 years ago
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>";
?>
up
-1
dj.luiting(.a.t.)gmail.com
9 months ago
hi folks, i struggled for a day to get a big decimal number converted into binary, on the windows platform.
finally with bcmath functions this is what worked for me.

function bc_convert2bin($string) {

    //got it to work with bcmath functions, works for 64 bit on 32 bit windows machine
    $finished=0;
    $base=2;
    $bin_nr='';

    if(preg_match("/[^0-9]/", $string)) {
        for($i=0; $string!=chr($i); $i++) {
            $dec_nr=$i;
        }
    } else {
        $dec_nr=$string;
    }
    //while( $dec_nr>$base ) {
    while( bccomp($dec_nr,$base) == 1 ) {

        //$base=$base*2;
        $base=bcmul($base,'2');
        //if($base>$dec_nr) {
        if( bccomp($base,$dec_nr) == 1 ) {
            //$base=$base/2;
            $base=bcdiv($base,'2');
            break;
        }
    }

    while(!$finished) {

        //if(($dec_nr-$base)>0) {
        if( bccomp( bcsub($dec_nr,$base) , 0) == 1 ) {

            //$dec_nr=$dec_nr-$base;
            $dec_nr=bcsub($dec_nr,$base);
            $bin_nr.=1;
            //$base=$base/2;
            $base=bcdiv($base,'2');

        //} elseif(($dec_nr-$base)<0) {
        } elseif( bccomp( bcsub($dec_nr,$base) , 0) == -1 ) {

            $bin_nr.=0;
            //$base=$base/2;
            $base=bcdiv($base,'2');

        //} elseif(($dec_nr-$base)==0) {
        } elseif( bccomp( bcsub($dec_nr,$base) , 0) == 0 ) {

            $bin_nr.=1;
            $finished=1;
            //while($base>1) {
            while( bccomp($base,1) == 1 ) {

                $bin_nr.=0;
                //$base=$base/2;
                $base=bcdiv($base,'2');

            }
        }
    }
    return $bin_nr;
}
up
-1
darkshad3 at yahoo dot com
7 years ago
<?php
Print bindecValues("1023");

function
bindecValues($decimal, $reverse=false, $inverse=false) {
/*
1. This function takes a decimal, converts it to binary and returns the
     decimal values of each individual binary value (a 1) in the binary string.
     You can use larger decimal values if you pass them to the function as a string!
2. The second optional parameter reverses the output.
3. The third optional parameter inverses the binary string, eg 101 becomes 010.
-- darkshad3 at yahoo dot com
*/

   
$bin = decbin($decimal);
    if (
$inverse) {
       
$bin = str_replace("0", "x", $bin);
       
$bin = str_replace("1", "0", $bin);
       
$bin = str_replace("x", "1", $bin);
    }
   
$total = strlen($bin);
   
   
$stock = array();
   
    for (
$i = 0; $i < $total; $i++) {
        if (
$bin{$i} != 0) {
           
$bin_2 = str_pad($bin{$i}, $total - $i, 0);
           
array_push($stock, bindec($bin_2));
        }
    }
   
   
$reverse ? rsort($stock):sort($stock);
    return
implode(", ", $stock);
}
?>

The printed result is : 1, 2, 4, 8, 16, 32, 64, 128, 256, 512
up
-1
Silas R (15)
1 year ago
This is my System:

You can convert a decimal number to a number system you want, like the binary system.

<?php
   
   
function Dec2oSys($numberDec, $SysNum)
    {
        if(
$numberDec != 0)
        {
           
$numberOSys = "";
            for (;
$numberDec > 0;) {
               
$numberDecBefore = $numberDec;
               
$numberDec = $numberDec / $SysNum;
               
$pos = strpos($numberDec, '.');
                if(
$pos != false)
                {
                   
$numberDec = floor($numberDec);
                   
$numberOSys .= $numberDecBefore - floor($numberDec) * $SysNum;
                   
$rest = $numberDecBefore - floor($numberDec) * $SysNum;
                }
                else
                {
                   
$numberOSys .= "0";
                   
$rest = 0;
                   
                }
                print
$numberDec."; Rest:".$rest."<br/>";
            }
        }
        else
        {
           
$numberOSys = "0";
        }
        return
strrev($numberOSys);
    }
   
    print
Dec2oSys(100, 2);
   
?>
up
-1
Kay
6 years ago
I think this is the best function. Is almost endlessy (till 2^50 or something)

<?php
function bin($int)
{
   
$i = 0;
   
$binair = "";
    while(
$int >= pow(2,$i))
    {
       
$i++;
    }
   
    if(
$i != 0)
    {
       
$i = $i-1; //max i
   
}

    while(
$i >= 0)
    {
        if(
$int - pow(2,$i) < 0)
        {
           
$binair = "0".$binair;
        }else{
           
$binair = "1".$binair;
           
$int = $int - pow(2,$i);
        }
       
       
$i--;
    }
    return
$binair;
}

$getal = $_GET['getal'];

   
echo
bin($getal);
?>
up
-1
php at silisoftware dot com
12 years ago
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;
}
up
-2
avenger at avenger dot ws
6 years ago
Careful trying binary-wise tests with integers:

# FFFFFFFF
command: php -r 'print(decbin(4294967295)."\n");'
result: 11111111111111111111111111111111

# C3E9CAC8
command: php -r 'print(decbin(3286878920)."\n");'
result: 11000011111010011100101011001000

# regardless of specifying "(int)", using bitwise AND:
command: php -r 'print((int)(3286878920 & 4294967295)."\n");'
result: -1008088376 (int)

# now the expected result will happen (guess the performance impact)
command: php -r 'print(bindec(decbin((3286878920 & 4294967295)))."\n");'
result: 3286878920 (float)

additional note: if you "bitwise and" some random bits with a sequence of 1-bit of the same length, the expected result is the same "random bits sequence" unchanged. If you want to keep this in the integer world for faster comparisons, you risk messing your result for the signed integer size limitation. The maximum value you can use for the desired result is (7FFFFFFF -- or integer 2147483647), half of the maximum 'unsigned' integer 32-bit(platform-dependent) value.
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