PHPerKaigi 2025

    bindec

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

    bindec — Da binario a decimale

    Descrizione

    bindec(string $stringa_binaria): int

    Restituisce il decimale equivalente al numero binario rappresentato dall'argomento stringa_binaria.

    bindec() converte un binario in integer. Il più grande numero che può essere convertito è 31 volte la cifra 1 oppure 2147483647 espresso in formato decimale.

    Example #1 Esempio di bindec()

    <?php
    echo bindec('110011') . "\n";
    echo     bindec('000110011') . "\n";

    echo     bindec('111');
    ?>

    L'esempio precedente visualizzerà: 

     
51 
51 
7

    Vedere anche decbin(), octdec(), hexdec() e base_convert().

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    User Contributed Notes 5 notes

    up
    7
    info at rickdg dot nl
    14 years ago
    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;
    }
    }     ?>
    up
    3
    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)
    up
    3
    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));
    }
    up
    2
    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.
    up
    1
    alan hogan dot com slash contact
    17 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);
    }
    ?>
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