decbin

    (PHP 4, PHP 5, PHP 7, PHP 8)

    decbin — Decimal to binary

    Description

    decbin(int $num): string

    Returns a string containing a binary representation of the given num argument.

    Parameters

    num

    Decimal value to convert

    Range of inputs on 32-bit machines
    positive num negative num return value
    0   0
    1   1
    2   10
    ... normal progression ...
    2147483646   1111111111111111111111111111110
    2147483647 (largest signed integer)   1111111111111111111111111111111 (31 1's)
    2147483648 -2147483648 10000000000000000000000000000000
    ... normal progression ...
    4294967294 -2 11111111111111111111111111111110
    4294967295 (largest unsigned integer) -1 11111111111111111111111111111111 (32 1's)
    Range of inputs on 64-bit machines
    positive num negative num return value
    0   0
    1   1
    2   10
    ... normal progression ...
    9223372036854775806   111111111111111111111111111111111111111111111111111111111111110
    9223372036854775807 (largest signed integer)   111111111111111111111111111111111111111111111111111111111111111 (63 1's)
      -9223372036854775808 1000000000000000000000000000000000000000000000000000000000000000
    ... normal progression ...
      -2 1111111111111111111111111111111111111111111111111111111111111110
      -1 1111111111111111111111111111111111111111111111111111111111111111 (64 1's)

    Return Values

    Binary string representation of num

    Examples

    Example #1 decbin() example

    <?php
    echo decbin(12) . "\n";
    echo     decbin(26);
    ?>

    The above example will output:

    1100
11010

    See Also

    • bindec() - Binary to decimal
    • decoct() - Decimal to octal
    • dechex() - Decimal to hexadecimal
    • base_convert() - Convert a number between arbitrary bases
    • printf() - Output a formatted string, using %b, %032b or %064b as the format
    • sprintf() - Return a formatted string, using %b, %032b or %064b as the format

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    User Contributed Notes 9 notes

    up
    26
    MarcelG
    10 years ago
    To add leading zeros I prefer the following:
    <?php
    // Add leading zeros
    $bin = sprintf( "%08d", decbin( 26 )); // "00011010"
    ?>
    up
    7
    rambabusaravanan at gmail dot com
    8 years ago
    Print as binary format with leading zeros into a variable in one simple statement.

    <?php
    $binary     = sprintf('%08b', $decimal); // $decimal = 5;
    echo $binary; // $binary = "00000101";
    ?>
    up
    7
    Xavier Daull
    18 years ago
    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

    ?>
    up
    4
    coverup
    7 years ago
    Regarding trailing zeros, after test all the option mention here by others, i have performed my own tests regarding efficiency, here are the results:

    <?php

    $decimal     = 9;

    $time_start = microtime(true);
    for (    $i=0;$i<1000;$i++){
    $bin = printf('%08b', $decimal);
    }
    $time_end = microtime(true);
    $time = $time_end - $time_start;
    echo     "<hr>Duracion $time segundos<br>\n";
    echo     $bin . '<br>';

    $time_start = microtime(true);
    for (    $i=0;$i<1000;$i++){
    $bin = sprintf( "%08d", decbin( $decimal ));
    }
    $time_end = microtime(true);
    $time = $time_end - $time_start;
    echo     "<hr>Duracion $time segundos<br>\n";
    echo     $bin . '<br>';

    $time_start = microtime(true);
    for (    $i=0;$i<1000;$i++){
    $bin = decbin($decimal);
    $bin = substr("00000000",0,8 - strlen($bin)) . $bin;
    }
    $time_end = microtime(true);
    $time = $time_end - $time_start;
    echo     "<hr>Duracion $time segundos<br>\n";
    echo     $bin . '<br>';

    ?>

    results

    0000100100001001000010010000100.... (output is echoed 1000 times)
    Duracion 0.0134768486023 segundos
    8
    Duracion 0.00054407119751 segundos
    00001001
    Duracion 0.000833988189697 segundos
    00001001

    Thus the winner is
    <?php
    $bin     = sprintf( "%08d", decbin( $decimal ));
    ?>
    up
    4
    noname at example dot com
    9 years ago
    If you want leading zeros use php built-in features instead of custom functions

    <?php
    printf    ('%08b', $decimal);
    ?>

    >> printf('%08b', E_NOTICE)
    >> 00001000
    up
    6
    Anonymous
    19 years ago
    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.
    up
    1
    dj.luiting(.a.t.)gmail.com
    10 years ago
    hi folks, i struggled for a day to get a big decimal number converted into binary, on the windows platform.
    finally with bcmath functions this is what worked for me.

    function bc_convert2bin($string) {

    //got it to work with bcmath functions, works for 64 bit on 32 bit windows machine
    $finished=0;
    $base=2;
    $bin_nr='';

    if(preg_match("/[^0-9]/", $string)) {
    for($i=0; $string!=chr($i); $i++) {
    $dec_nr=$i;
    }
    } else {
    $dec_nr=$string;
    }
    //while( $dec_nr>$base ) {
    while( bccomp($dec_nr,$base) == 1 ) {

    //$base=$base*2;
    $base=bcmul($base,'2');
    //if($base>$dec_nr) {
    if( bccomp($base,$dec_nr) == 1 ) {
    //$base=$base/2;
    $base=bcdiv($base,'2');
    break;
    }
    }

    while(!$finished) {

    //if(($dec_nr-$base)>0) {
    if( bccomp( bcsub($dec_nr,$base) , 0) == 1 ) {

    //$dec_nr=$dec_nr-$base;
    $dec_nr=bcsub($dec_nr,$base);
    $bin_nr.=1;
    //$base=$base/2;
    $base=bcdiv($base,'2');

    //} elseif(($dec_nr-$base)<0) {
    } elseif( bccomp( bcsub($dec_nr,$base) , 0) == -1 ) {

    $bin_nr.=0;
    //$base=$base/2;
    $base=bcdiv($base,'2');

    //} elseif(($dec_nr-$base)==0) {
    } elseif( bccomp( bcsub($dec_nr,$base) , 0) == 0 ) {

    $bin_nr.=1;
    $finished=1;
    //while($base>1) {
    while( bccomp($base,1) == 1 ) {

    $bin_nr.=0;
    //$base=$base/2;
    $base=bcdiv($base,'2');

    }
    }
    }
    return $bin_nr;
    }
    up
    1
    php at silisoftware dot com
    22 years ago
    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;
    }
    up
    0
    malcolm.murphy
    7 years ago
    The GNU MP library (http://php.net/manual/en/book.gmp.php) provides methods to efficiently convert binary strings of any length to their binary representation (i.e., a `decbin` equivalent for strings).

    <?php

    $str     = random_bytes(1024); // binary string example

    $result = gmp_strval(gmp_import($str), 2); // see manual for options such as endianness

    $zeroPadded = sprintf('%0' . (strlen($str) * 8) . 's', $result); // zero-pad if needed, e.g. with str_pad, or sprintf as shown here

    $strAgain = gmp_export(gmp_init($result, 2)); // reverse operation similar to bindec

    ?>
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