decbin()

(PHP 4, PHP 5, PHP 7)

十进制转换为二进制

说明

decbin(int $number): string

返回一字符串，包含有给定$number参数的二进制表示。所能转换的最大数值为十进制的 4294967295，其结果为 32 个 1 的字符串。

参数

$number

Decimal value to convert

Range of inputs on 32-bit machines

positive$number	negative$number	return value
0		0
1		1
2		10
... normal progression ...
2147483646		1111111111111111111111111111110
2147483647 (largest signed integer)		1111111111111111111111111111111 (31 1's)
2147483648	-2147483648	10000000000000000000000000000000
... normal progression ...
4294967294	-2	11111111111111111111111111111110
4294967295 (largest unsigned integer)	-1	11111111111111111111111111111111 (32 1's)

Range of inputs on 64-bit machines

positive$number	negative$number	return value
0		0
1		1
2		10
... normal progression ...
9223372036854775806		111111111111111111111111111111111111111111111111111111111111110
9223372036854775807 (largest signed integer)		111111111111111111111111111111111111111111111111111111111111111 (63 1's)
	-9223372036854775808	1000000000000000000000000000000000000000000000000000000000000000
... normal progression ...
	-2	1111111111111111111111111111111111111111111111111111111111111110
	-1	1111111111111111111111111111111111111111111111111111111111111111 (64 1's)

返回值

Binary string representation of$number

范例

Example #1decbin()例子

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

以上例程会输出：

1100
11010

参见

• bindec() 二进制转换为十进制
• decoct() 十进制转换为八进制
• dechex() 十进制转换为十六进制
• base_convert() 在任意进制之间转换数字
• printf() 输出格式化字符串,using%b,%032bor%064bas the format
• sprintf(),using%b,%032bor%064bas the format

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

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
?>

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 ));
?>

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";
?>

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;
}

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.

If you want leading zeros use php built-in features instead of custom functions
<?php
printf('%08b', $decimal);
?>
>> printf('%08b', E_NOTICE)
>> 00001000

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
?>

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.

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;
}

<?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

base_convert( base_convert('100001000100000000010001001000
0100100000001111111111111111111',2,10),10,2);
return
'1000010001000000000100010010000
100100000010000000000000000000'
this function doesn't work

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>";
?>

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

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);
  
?>

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.

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);
?>