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decbin

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

decbin10 進数を 2 進数に変換する

説明

decbin(int $num): string

引数 num を 2 進数表現した文字列を返します。

パラメータ

num

変換したい 10 進数値。

32 ビットマシンでの入力の範囲
正の num 負の num 戻り値
0   0
1   1
2   10
... normal progression ...
2147483646   1111111111111111111111111111110
2147483647 (符号付き integer の最大値)   1111111111111111111111111111111 (1 が 31 個)
2147483648 -2147483648 10000000000000000000000000000000
... normal progression ...
4294967294 -2 11111111111111111111111111111110
4294967295 (符号なし integer の最大値) -1 11111111111111111111111111111111 (1 が 32 個)
64 ビットマシンでの入力の範囲
正の num 負の num 戻り値
0   0
1   1
2   10
... normal progression ...
9223372036854775806   111111111111111111111111111111111111111111111111111111111111110
9223372036854775807 (符号付き integer の最大値)   111111111111111111111111111111111111111111111111111111111111111 (1 が 63 個)
  -9223372036854775808 1000000000000000000000000000000000000000000000000000000000000000
... normal progression ...
  -2 1111111111111111111111111111111111111111111111111111111111111110
  -1 1111111111111111111111111111111111111111111111111111111111111111 (1 が 64 個)

戻り値

num を 2 進文字列で表した値を返します。

例1 decbin() の例

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

上の例の出力は以下となります。

1100
11010

参考

  • bindec() - 2 進数 を 10 進数に変換する
  • decoct() - 10 進数を 8 進数に変換する
  • dechex() - 10 進数を 16 進数に変換する
  • base_convert() - 数値の基数を任意に変換する
  • printf() - フォーマット済みの文字列を出力する でのフォーマット %b%032b あるいは %064b
  • sprintf() - フォーマットされた文字列を返す でのフォーマット %b%032b あるいは %064b

add a note

User Contributed Notes 14 notes

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29
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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6
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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5
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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7
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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6
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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3
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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1
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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1
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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1
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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