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decbin — Dezimal zu Binär Konvertierung
Liefert eine binäre Representation des Parameters number als String. Der größte konvertierbare Wert ist dezimal 4294967295 bzw. eine Kette von 32 einsen im Binärergebnis.
Der umzuwandelnde Dezimalwert
Binärrepresentation von number als String.
Beispiel #1 decbin() Beispiel
<?php
echo decbin(12) . "\n";
echo decbin(26);
?>
Das oben gezeigte Beispiel erzeugt folgende Ausgabe:
1100 11010
Here's a simple decbin function that uses BC Math. It works only for positive numbers and has no upper limit for $dec (except computation time).
<?php
function bcdecbin($dec) {
$bin = '';
while ($dec) {
$m = bcmod($dec, 2);
$dec = bcdiv($dec, 2);
$bin .= abs($m);
}
return strrev($bin);
}
?>
I was surprised by decbin's size limitation. Here is a function without size limitation. It supports much bigger values (like 11.435.168.214), but doesn't support signs because I didn't need signs (yet).
<?php
function dec2bin($dec){
// Better function for dec to bin. Support much bigger values, but doesn’t support signs
for($b='',$r=$dec;$r>1;){
$n = floor($r/2); $b = ($r-$n*2).$b; $r = $n; // $r%2 is inaccurate when using bigger values (like 11.435.168.214)!
}
return ($r%2).$b;
}
?>
Decimal to Binary conversion using the BCMath extension.
<?php
function BCDec2Bin($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.
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);
?>
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.
<?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(", ", $stock);
}
?>
The printed result is : 1, 2, 4, 8, 16, 32, 64, 128, 256, 512
I wrote the decoder for the output of Xavier Daull's function "BinString2BinSequence".
<?php
function bs2string($bitseq) {
if (strlen($bitseq) % 8 != 0) return false;
$str = "";
$bitseqlen = strlen($bitseq);
for($i = 0; $i < $bitseqlen; $i += 8) {
$str .= chr(bindec(substr($bitseq,$i,8)));
}
return $str;
}
?>
Have fun
A fast function to convert a binary string to a bit sequence
<?php
function BinString2BitSequence($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
?>
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)) . $bin;
This will convert 11010 to 00011010.
It occured to me there must be a simple way to produce binary numbers from decimal ones with any number of bits, here's my attempt at a decimal to extended binary function. I hope the comments make it clear:
<?php
function decextbin($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($i,4).'<br />';
}
?>
Output:
0000
0001
0010
0011
0100
0101
0110
0111
1000
No need for padding or anything - also goes way over 32 bits. Huzzah. I suspect its limited by the maximum string length in php. Hmmm - Not sure what that is.
matt at nexxmedia dot com (06-Dec-2002 04:29) said:
<?php
...
strrev(str_pad(decbin($decval),8,"0",STR_PAD_LEFT));
...
?>
<?php
str_pad(decbin ($decval),8,'0');
?>
produces the same results!
base_convert( base_convert('100001000100000000010001001000
0100100000001111111111111111111',2,10),10,2);
return
'1000010001000000000100010010000
100100000010000000000000000000'
this function doesn't work
<?php // function for converting values >= 2147483648 (2^16)
function decbin4long($long) {
return base_convert($long,10,2);
} // idea from http://phpclub.ru/talk/showthread.php?postid=407488
?>
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 $bitarray;
}
Another larger-than-31-bit function.
Works for very large numbers, but at the expense of perfect bit-precision as the size increases (I noticed rounding errors past 16 or so decimal places) so use with caution, and only when decbin() won't cut it.
function Dec2Bin($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 $binstring;
}
HERE you can convert 64bit instead of 32bit with the standard decbin
<?
function bigdecbin($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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