decbin

(PHP 4, PHP 5, PHP 7, PHP 8)

decbin — Da decimale a binario

Descrizione

decbin(int $numero): string

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 17 notes

down

MarcelG ¶

10 years ago


To add leading zeros I prefer the following:
<?php
// Add leading zeros
$bin = sprintf( "%08d", decbin( 26 )); // "00011010"
?>

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rambabusaravanan at gmail dot com ¶

7 years ago


Print as binary format with leading zeros into a variable in one simple statement.

<?php
    $binary = sprintf('%08b',  $decimal);    // $decimal = 5;
    echo $binary;    // $binary = "00000101";
?>

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Xavier Daull ¶

18 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

?>

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coverup ¶

7 years ago


Regarding trailing zeros, after test all the option mention here by others, i have performed my own tests regarding efficiency, here are the results:

<?php

$decimal = 9;

$time_start = microtime(true);
for ($i=0;$i<1000;$i++){
$bin = printf('%08b',  $decimal);
}
$time_end = microtime(true);
$time = $time_end - $time_start;
echo "<hr>Duracion $time segundos<br>\n";
echo $bin . '<br>';

$time_start = microtime(true);
for ($i=0;$i<1000;$i++){
$bin = sprintf( "%08d", decbin( $decimal ));
}
$time_end = microtime(true);
$time = $time_end - $time_start;
echo "<hr>Duracion $time segundos<br>\n";
echo $bin . '<br>';

$time_start = microtime(true);
for ($i=0;$i<1000;$i++){
$bin = decbin($decimal);
$bin = substr("00000000",0,8 - strlen($bin)) . $bin;
}
$time_end = microtime(true);
$time = $time_end - $time_start;
echo "<hr>Duracion $time segundos<br>\n";
echo $bin . '<br>';

?>

results

0000100100001001000010010000100.... (output is echoed 1000 times)
Duracion 0.0134768486023 segundos
8
Duracion 0.00054407119751 segundos
00001001
Duracion 0.000833988189697 segundos
00001001

Thus the winner is 
<?php
$bin = sprintf( "%08d", decbin( $decimal ));
?>

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Anonymous ¶

18 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.

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noname at example dot com ¶

9 years ago


If you want leading zeros use php built-in features instead of custom functions

<?php
printf('%08b',  $decimal);
?>

>> printf('%08b', E_NOTICE)
>> 00001000

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dj.luiting(.a.t.)gmail.com ¶

10 years 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;
}

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malcolm.murphy ¶

7 years ago


The GNU MP library (http://php.net/manual/en/book.gmp.php) provides methods to efficiently convert binary strings of any length to their binary representation (i.e., a `decbin` equivalent for strings).

<?php

$str = random_bytes(1024); // binary string example

$result = gmp_strval(gmp_import($str), 2); // see manual for options such as endianness

$zeroPadded = sprintf('%0' . (strlen($str) * 8) . 's', $result); // zero-pad if needed, e.g. with str_pad, or sprintf as shown here

$strAgain = gmp_export(gmp_init($result, 2)); // reverse operation similar to bindec

?>

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php at silisoftware dot com ¶

22 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;
}

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-1

Nitrogen ¶

15 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.

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-1

mcampa at gmail dot com ¶

11 years 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

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-1

ajl at gmx dot de ¶

23 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>";

?>

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-2

darkshad3 at yahoo dot com ¶

17 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

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-2

Anonymous ¶

19 years ago


base_convert( base_convert('100001000100000000010001001000
0100100000001111111111111111111',2,10),10,2);

return
'1000010001000000000100010010000
100100000010000000000000000000'

this function doesn't work

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-6

avenger at avenger dot ws ¶

16 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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-6

Silas R (15) ¶

11 years 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);
    
?>

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-9

Kay ¶

16 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);
?>

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