PHP: bindec - Manual

Description

number bindec ( string binary_string )

Returns the decimal equivalent of the binary number represented by the binary_string argument.

bindec() converts a binary number to an integer. The largest number that can be converted is 31 bits of 1's or 2147483647 in decimal. As of PHP 4.1.0, this function can also convert larger numbers. It returns float in that case.

Пример 1. bindec() example

<?php echo bindec('110011') . "\n"; echo bindec('000110011') . "\n"; echo bindec('111'); ?>
Результат выполнения данного примера:
51 51 7

bindec

26-Aug-2004 02:42


decbin('1001') is prefered as decbin(1001). 



Because on larger bit string, it may cause problem :



decbin(100000000000000) return 3

else

decbin('100000000000000') return 16384

gwbdome at freenet dot de
19-Aug-2004 02:43


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 10:47


## 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)

juancri at tagnet dot org
30-Oct-2002 04:16


> The special reason 4 this is:

> (010) is an integer, left 0 is null, eg 010 = 10

> ('010') is a string, eg '010' = '010'



In binary, just like with decimals, the left 0's are nulls.



in Decimal:  010 = 10

in Binary:    010 = 10 too :o)



> echo decbin(bindec(010010010)); 

> returns 101000 



010010010 is a octal number. It's eq. to 2101256 (decimal). decbin(bindec(010010010)) is 101000 because 010010010 = 2101256.



That's all =)

php at silisoftware dot com
28-Feb-2002 07:16


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;


}


?>

da_he4datthe-gurusdotde
16-Sep-2001 07:11


[Editor's Note:


Numeric values starting with 0 are interpreted as octal (base eight) values.  For example: 0101 is converts to 65


--zak@php.net]





i was quite confused while werking with those bindec()/decbin() functions..


while


echo decbin(bindec(1));


echo decbin(bindec(10));


echo decbin(bindec(101));


just worked like expected,


echo decbin(bindec(010));


returns just 0


and for any reason


echo decbin(bindec(010010010));


returns 101000





i dont think this is a bug (maybe theres some special reason 4 this?), but it took  a certain time till i noticed that


echo decbin(bindec("010010010"));


works fine ...





hope this helps ne1.