bindec

说明

number bindec ( string binary_string )

返回 binary_string 参数所表示的二进制数的十进制等价值。

bindec() 将一个二进制数转换成 integer。可转换的最大的数为 31 位 1 或者说十进制的 2147483647。PHP 4.1.0 开始，该函数可以处理大数值，这种情况下，它会返回 float 类型。

例子 1. bindec() 范例
<?php echo bindec('110011') . "\n"; echo bindec('000110011') . "\n"; echo bindec('111'); ?>
上例将输出：
51 51 7

参见 decbin()，octdec()，hexdec() 和 base_convert()。

add a note User Contributed Notes

26-Aug-2004 05:42


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
20-Aug-2004 05:43


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
30-May-2003 01:47


## 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 08:16


> 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
01-Mar-2002 11:16


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
17-Sep-2001 10:11


[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.

add a note