base_convert
Two functions to convert 16bit or 8bit binary to integer using two's complement. If input exceeds maximum bits, false is returned. Function is easily scalable to x bits by changing the hexadecimals.
<?php function _bin16dec($bin) {
// Function to convert 16bit binary numbers to integers using two's complement
$num = bindec($bin);
if($num > 0xFFFF) { return false; }
if($num >= 0x8000) {
return -(($num ^ 0xFFFF)+1);
} else {
return $num;
}
}
function _bin8dec($bin) {
// Function to convert 8bit binary numbers to integers using two's complement
$num = bindec($bin);
if($num > 0xFF) { return false; }
if($num >= 0x80) {
return -(($num ^ 0xFF)+1);
} else {
return $num;
}
} ?>
bindec
(PHP 4, PHP 5)
bindec — 2 進数 を 10 進数に変換する
説明
引数 binary_string により指定された
2 進数と等価な 10 進数を返します。
bindec() は、2 進数を integer に変換します。 サイズの問題により、必要に応じて float となることもあります。
bindec() は、すべての
binary_string 値を符号なし整数として扱います。
これは、bindec() が最上位ビットを
符号ビットとしてではなく規模をはかるためのに使用するからです。
パラメータ
-
binary_string -
変換したい 2 進数文字列。
警告
このパラメータは文字列でなければなりません。 他のデータ型を使用すると、予期せぬ結果となります。
返り値
binary_string を 10 進に変換した値を返します。
例
例1 bindec() の例
<?php
echo bindec('110011') . "\n";
echo bindec('000110011') . "\n";
echo bindec('111');
?>
上の例の出力は以下となります。
51 51 7
例2 bindec() が入力を符号なし整数として処理する例
<?php
/*
* The lesson from this example is in the output
* rather than the PHP code itself.
*/
$magnitude_lower = pow(2, (PHP_INT_SIZE * 8) - 2);
p($magnitude_lower - 1);
p($magnitude_lower, 'See the rollover? Watch it next time around...');
p(PHP_INT_MAX, 'PHP_INT_MAX');
p(~PHP_INT_MAX, 'interpreted to be one more than PHP_INT_MAX');
if (PHP_INT_SIZE == 4) {
$note = 'interpreted to be the largest unsigned integer';
} else {
$note = 'interpreted to be the largest unsigned integer
(18446744073709551615) but skewed by float precision';
}
p(-1, $note);
function p($input, $note = '') {
echo "input: $input\n";
$format = '%0' . (PHP_INT_SIZE * 8) . 'b';
$bin = sprintf($format, $input);
echo "binary: $bin\n";
ini_set('precision', 20); // For readability on 64 bit boxes.
$dec = bindec($bin);
echo 'bindec(): ' . $dec . "\n";
if ($note) {
echo "NOTE: $note\n";
}
echo "\n";
}
?>
上の例の 32 ビットマシンでの出力は、このようになります。
input: 1073741823 binary: 00111111111111111111111111111111 bindec(): 1073741823 input: 1073741824 binary: 01000000000000000000000000000000 bindec(): 1073741824 NOTE: See the rollover? Watch it next time around... input: 2147483647 binary: 01111111111111111111111111111111 bindec(): 2147483647 NOTE: PHP_INT_MAX input: -2147483648 binary: 10000000000000000000000000000000 bindec(): 2147483648 NOTE: interpreted to be one more than PHP_INT_MAX input: -1 binary: 11111111111111111111111111111111 bindec(): 4294967295 NOTE: interpreted to be the largest unsigned integer
上の例の 64 ビットマシンでの出力は、このようになります。
input: 4611686018427387903
binary: 0011111111111111111111111111111111111111111111111111111111111111
bindec(): 4611686018427387903
input: 4611686018427387904
binary: 0100000000000000000000000000000000000000000000000000000000000000
bindec(): 4611686018427387904
NOTE: See the rollover? Watch it next time around...
input: 9223372036854775807
binary: 0111111111111111111111111111111111111111111111111111111111111111
bindec(): 9223372036854775807
NOTE: PHP_INT_MAX
input: -9223372036854775808
binary: 1000000000000000000000000000000000000000000000000000000000000000
bindec(): 9223372036854775808
NOTE: interpreted to be one more than PHP_INT_MAX
input: -1
binary: 1111111111111111111111111111111111111111111111111111111111111111
bindec(): 18446744073709551616
NOTE: interpreted to be the largest unsigned integer
(18446744073709551615) but skewed by float precision
参考
- decbin() - 10 進数を 2 進数に変換する
- octdec() - 8 進数を 10 進数に変換する
- hexdec() - 16 進数を 10 進数に変換する
- base_convert() - 数値の基数を任意に変換する
add a note
User Contributed Notes
bindec
info at rickdg dot nl
31-Mar-2010 10:40
Nitrogen
21-Jul-2009 01:27
Binary to Decimal conversion using the BCMath extension..
<?php
function BCBin2Dec($Input='') {
$Output='0';
if(preg_match("/^[01]+$/",$Input)) {
for($i=0;$i<strlen($Input);$i++)
$Output=BCAdd(BCMul($Output,'2'),$Input{$i});
}
return($Output);
}
?>
This will simply convert from Base-2 to Base-10 using BCMath (arbitrary precision calculation).
See also: my 'BCDec2Bin' function on the 'decbin' document.
Enjoy,
Nitrogen.
nodarinodo at mail dot ru
08-Jan-2009 04:51
<?php
// bindecfunc :)))) I think it works well too :)
function bindecc($str)
{
$str = str_replace(" ", "", $str);
$strr = preg_match('/[^01]/', $str);
if($strr == 1) { return "<b> Error ! only 1 and 0;</b>"; }
$strsig = strlen($str);
$strr1 = strrev($str);
$strf = '';
for($i = $strsig; $i >= 0; $i--)
{
$strf += ($strr1[$i] * pow(2, $i));
#$strf += $str[$i];
}
return $strf;
}
?>
flashpack at gmail dot com
15-Nov-2008 09:40
for converting fractions :
eg : 1001.1101
<?php
function BinaryToDecimal($binary){
$binary=trim($binary);
if (strstr($binary,'.')){
$split=explode('.',$binary);
$integer=$split[0];
$fraction=$split[1];
$digits=str_split($fraction);
$num=sizeof($digits);
for ($i=1; $i<=$num;$i++){
if ($digits[$i-1]>1){
echo '<script>alert("Enter Binary Digits Only {0,1}\n \n eg: 11001 or 11001.011");history.go(-1)</script> ';
}
$exponent=pow(2,-$i);
$fraction_result+=$digits[$i-1]*$exponent;
}
}else{
$integer=$binary;
}
$splits=str_split($integer);
$num=sizeof($splits)-1;
$i=$num;
foreach($splits as $digits){
if ($digits>1){
echo '<script>alert("Enter Binary Digits Only {0,1}\n \n eg: 11001 or 11001.011");history.go(-1)</script> ';
}
$exponent=pow(2,$i);
$integer_result+=$digits*$exponent;
$i--;
}
if($fraction_result){
$result=$integer_result+$fraction_result;
}else {
$result=$integer_result;
}
return $result ;
}
?>
mashematician at gmail dot com
13-Mar-2008 02:57
A binary to decimal conversion function that takes advantage of the BC library functions to return decimal values of arbitrary length.
Input type must be a string in order to work properly.
<?php
function binary_to_decimal($a) {
$bin_array = str_split($a);
$y=sizeof($bin_array)-1;
for ($x=0; $x<sizeof($bin_array)-1; $x++) {
if ($bin_array[$x] == 1) {
$bin_array[$x] = bcpow(2, $y);
}
$y--;
}
for ($z=0; $z<sizeof($bin_array); $z++) {
$result = bcadd($result, $bin_array[$z]);
}
echo $result;
}
binary_to_decimal('11111');
?>
alan hogan dot com slash contact
08-Nov-2007 06:34
The "smartbindec" function I wrote below will convert any binary string (of a reasonable size) to decimal. It will use two's complement if the leftmost bit is 1, regardless of bit length. If you are getting unexpected negative answers, try zero-padding your strings with sprintf("%032s", $yourBitString).
<?php
function twoscomp($bin) {
$out = "";
$mode = "init";
for($x = strlen($bin)-1; $x >= 0; $x--) {
if ($mode != "init")
$out = ($bin[$x] == "0" ? "1" : "0").$out;
else {
if($bin[$x] == "1") {
$out = "1".$out;
$mode = "invert";
}
else
$out = "0".$out;
}
}
return $out;
}
function smartbindec($bin) {
if($bin[0] == 1)
return -1 * bindec(twoscomp($bin));
else return (int) bindec($bin);
}
?>
gwbdome at freenet dot de
19-Aug-2004 08:43
i think a better method than the "shift-method" is my method ^^...
here it comes:
function convert2bin($string) {
$finished=0;
$base=1;
if(preg_match("/[^0-9]/", $string)) {
for($i=0; $string!=chr($i); $i++);
$dec_nr=$i;
}
else $dec_nr=$string;
while($dec_nr>$base) {
$base=$base*2;
if($base>$dec_nr) {
$base=$base/2;
break;
}
}
while(!$finished) {
if(($dec_nr-$base)>0) {
$dec_nr=$dec_nr-$base;
$bin_nr.=1;
$base=$base/2;
}
elseif(($dec_nr-$base)<0) {
$bin_nr.=0;
$base=$base/2;
}
elseif(($dec_nr-$base)==0) {
$bin_nr.=1;
$finished=1;
while($base>1) {
$bin_nr.=0;
$base=$base/2;
}
}
}
return $bin_nr;
}
=====================================================
if you want to reconvert it (from binary to string or integer) you can use this function:
function reconvert($bin_nr) {
$base=1;
$dec_nr=0;
$bin_nr=explode(",", preg_replace("/(.*),/", "$1", str_replace("1", "1,", str_replace("0", "0,", $bin_nr))));
for($i=1; $i<count($bin_nr); $i++) $base=$base*2;
foreach($bin_nr as $key=>$bin_nr_bit) {
if($bin_nr_bit==1) {
$dec_nr+=$base;
$base=$base/2;
}
if($bin_nr_bit==0) $base=$base/2;
}
return(array("string"=>chr($dec_nr), "int"=>$dec_nr));
}
martin at punix dot de
29-May-2003 04:47
## calculate binary with "shift-method" ##
<?php
function dec2bin($decimal_code){
for($half=($decimal_code);$half>=1;$half=(floor($half))/2){
if(($half%2)!=0){
$y.=1;
}
else{
$y.=0;
}
}
$calculated_bin=strrev($y);
return $calculated_bin;
}
?>
## example ##
[bin] 123 = [dec] 1111011
e.g.
123/2 = 61,5 => 1
61/2 = 30,5 => 1
30/2 = 15 => 0
15/2 = 7,5 => 1
7/2 = 3,5 => 1
3/2 = 1,5 => 1
1/2 = 0,5 => 1
(0/2 = 0 finish)
php at silisoftware dot com
28-Feb-2002 12:16
For converting larger-than-31-bit numbers:
<?php
function Bin2Dec($binstring) {
for ($i=0;$i<strlen($binstring);$i++) {
$decvalue += ((int) substr($binstring, strlen($binstring) - $i - 1, 1)) * pow(2, $i);
}
return $decvalue;
}
?>