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, PHP 7, PHP 8)
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 int 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
符号ビットではなく別の桁とみなすからです。
パラメータ
-
binary_string -
変換したい 2 進数文字列。
binary_stringに無効な文字を与えても、静かに無視されます。 PHP 7.4.0 以降では、無効な文字を与えることは推奨されません。
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。
戻り値
binary_string を 10 進に変換した値を返します。
変更履歴
| バージョン | 説明 |
|---|---|
| 7.4.0 | 無効な文字を与えると、非推奨の警告が出るようになりました。 結果は不正な文字がなかったかのように計算されます。 |
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: $note\n";
}
echo "\n";
}
?>上の例の 32 ビットマシンでの出力は、このようになります。
input: 1073741823 binary: 00111111111111111111111111111111 bindec(): 1073741823 input: 1073741824 binary: 01000000000000000000000000000000 bindec(): 1073741824 NOTE: See the rollover? Watch it next time around... input: 2147483647 binary: 01111111111111111111111111111111 bindec(): 2147483647 NOTE: PHP_INT_MAX input: -2147483648 binary: 10000000000000000000000000000000 bindec(): 2147483648 NOTE: interpreted to be one more than PHP_INT_MAX input: -1 binary: 11111111111111111111111111111111 bindec(): 4294967295 NOTE: interpreted to be the largest unsigned integer
上の例の 64 ビットマシンでの出力は、このようになります。
input: 4611686018427387903
binary: 0011111111111111111111111111111111111111111111111111111111111111
bindec(): 4611686018427387903
input: 4611686018427387904
binary: 0100000000000000000000000000000000000000000000000000000000000000
bindec(): 4611686018427387904
NOTE: See the rollover? Watch it next time around...
input: 9223372036854775807
binary: 0111111111111111111111111111111111111111111111111111111111111111
bindec(): 9223372036854775807
NOTE: PHP_INT_MAX
input: -9223372036854775808
binary: 1000000000000000000000000000000000000000000000000000000000000000
bindec(): 9223372036854775808
NOTE: interpreted to be one more than PHP_INT_MAX
input: -1
binary: 1111111111111111111111111111111111111111111111111111111111111111
bindec(): 18446744073709551616
NOTE: interpreted to be the largest unsigned integer
(18446744073709551615) but skewed by float precision
参考
- decbin() - 10 進数を 2 進数に変換する
- octdec() - 8 進数を 10 進数に変換する
- hexdec() - 16 進数を 10 進数に変換する
- base_convert() - 数値の基数を任意に変換する
add a note
User Contributed Notes 10 notes
info at rickdg dot nl ¶
14 years ago
martin at punix dot de ¶
21 years ago
## calculate binary with "shift-method" ##
<?php
function dec2bin($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 $calculated_bin;
}
?>
## example ##
[bin] 123 = [dec] 1111011
e.g.
123/2 = 61,5 => 1
61/2 = 30,5 => 1
30/2 = 15 => 0
15/2 = 7,5 => 1
7/2 = 3,5 => 1
3/2 = 1,5 => 1
1/2 = 0,5 => 1
(0/2 = 0 finish)
gwbdome at freenet dot de ¶
20 years ago
i think a better method than the "shift-method" is my method ^^...
here it comes:
function convert2bin($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));
}
Nitrogen ¶
15 years ago
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.
alan hogan dot com slash contact ¶
16 years ago
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);
}
?>
patrick dot boens at latosensu dot be ¶
12 years ago
Left-shift a string by a number of bytes
<?php
function STR_shl( $szStr,$nBits )
/*-----------------------------*/
{
if ( $nBits < 1 || $nBits > 7 ) /* If not adequate number of bits */
{
return ( $szStr ); /* Return the original string */
} /* if ( $nBits < 1 || $nBits > 7 ) */
if ( ( $iLength = strlen( $szStr ) ) <= 0 ) /* If string empty */
{
return ( $szStr ); /* Return the original string */
} /* if ( ( $iLength = strlen( $szStr ) ) <= 0 ) */
$szRetVal = ''; /* Create an empty string */
$szBits = STR_Binary( $szStr ); /* $szStr in bits */
$szLostBits = STR_Left( $szBits,$nBits ); /* The $nBits leftmost bits of the string */
$szShifted = substr( $szBits,$nBits ) . $szLostBits; /* $szStr left shifted */
for ( $i = 0;$i < $iLength;$i++ ) /* Treat the entire string (per slice of 8 bits) */
{
$szRetVal .= chr( bindec( substr( $szShifted,$i * 8,8 ) ) ); /* Concatenate the CHR to the result string */
} /* for ( $i = 0;$i < $iLength;$i++ ) */
return ( $szRetVal ); /* Return result to caller */
}
?>
Right-shift a string by a number of bytes
<?php
function STR_shr( $szStr,$nBits )
/*-----------------------------*/
{
if ( $nBits < 1 || $nBits > 7 ) /* If not adequate number of bits */
{
return ( $szStr ); /* Return the original string */
} /* if ( $nBits < 1 || $nBits > 7 ) */
if ( ( $iLength = strlen( $szStr ) ) <= 0 ) /* If string empty */
{
return ( $szStr ); /* Return the original string */
} /* if ( ( $iLength = strlen( $szStr ) ) <= 0 ) */
$szRetVal = ''; /* Create an empty string */
$szBits = STR_Binary( $szStr ); /* $szStr in bits */
$szLostBits = STR_Right( $szBits,$nBits ); /* The $nBits rightmost bits of the string */
$szShifted = $szLostBits . substr( $szBits,0,-$nBits ); /* $szStr right shifted */
for ( $i = 0;$i < $iLength;$i++ ) /* Treat the entire string (per slice of 8 bits) */
{
$szRetVal .= chr( bindec( substr( $szShifted,$i * 8,8 ) ) ); /* Concatenate the CHR to the result string */
} /* for ( $i = 0;$i < $iLength;$i++ ) */
return ( $szRetVal ); /* Return result to caller */
}
?>
Additional functions used by the two preceding:
<?php
function STR_Binary( $szStr )
/*-------------------------*/
{
$szRetVal = ''; /* Ready to return an empty string */
if ( ( $iLength = strlen( $szStr ) ) > 0 ) /* If string NOT empty */
{
for ( $i = 0; $i < $iLength;$i++ ) /* Treat each character of the string */
{
$szRetVal .= sprintf( '%08b',ord( $szStr[$i] ) ); /* Turn this char to a binary representation (8 bits) */
} /* for ( $i = 0; $i < $iLength;$i++ ) */
} /* if ( ( $iLength = strlen( $szStr ) ) > 0 ) */
return ( $szRetVal ); /* Return result to caller */
}
function STR_Left( $szStr,$iCount = 1 )
/*----------------------------------*/
{
return substr( $szStr,0,$iCount );
} /* End of function strleft() */
function STR_Right( $szString,$iCount )
/*----------------------------------*/
{
return substr( $szString,0 + strlen( $szString ) - $iCount,$iCount );
}
?>
mashematician at gmail dot com ¶
16 years ago
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');
?>
jpfstange at gmail dot com ¶
8 years ago
<?php
//binfloat (For single precision floating point numbers)
//IEE754
//https://en.wikipedia.org/wiki/Single-precision_floating-point_format
function binfloat(Array $num){
$sign = $num[0] ? 1 : -1; //1 bit
$exponent = pow(2,bindec(implode('',array_slice($num,1,8)))-127);
$fraction = array_slice($num,9,count($num)); //23 bits
$fracSum = 1;
for($i=0;$i<23;$i++){
$fracSum += $fraction[$i] * pow(2,-1-$i);
}
return $fracSum*$exponent;
}
$num = isset($_GET['num']) ? $_GET['num'] : '00111110001000000000000000000000';
if(strlen($num)<32){
echo "Invalid binary number $num\n";
exit(1);
}
$num = str_split($num);
echo sprintf('Num is: [%s]%s',implode('',$num),"\n");
echo sprintf('Result is: %s%s',binfloat($num),"\n");
flashpack at gmail dot com ¶
15 years ago
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 $result ;
}
?>
nodarinodo at mail dot ru ¶
15 years ago
<?php
// bindecfunc :)))) I think it works well too :)
function bindecc($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;
}
?>
