php-doc-en/reference/math/functions/bindec.xml

<?xml version="1.0" encoding="utf-8"?>
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<refentry xml:id="function.bindec" xmlns="http://docbook.org/ns/docbook">
 <refnamediv>
  <refname>bindec</refname>
  <refpurpose>Binary to decimal</refpurpose>
 </refnamediv>
 <refsect1 role="description">
  &reftitle.description;
   <methodsynopsis>
    <type>number</type><methodname>bindec</methodname>
    <methodparam><type>string</type><parameter>binary_string</parameter></methodparam>
   </methodsynopsis>
  <para>
   Returns the decimal equivalent of the binary number represented by
   the <parameter>binary_string</parameter> argument.
  </para>
  <para>
   <function>bindec</function> converts a binary number to an
   <type>integer</type> or, if needed for size reasons, <type>float</type>.
  </para>
  <para>
   <function>bindec</function> interprets all
   <parameter>binary_string</parameter> values as unsigned
   integers. This is because <function>bindec</function> sees
   the most significant bit as another order of magnitude
   rather than as the sign bit.
  </para>
 </refsect1>
 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>binary_string</parameter></term>
     <listitem>
      <para>
       The binary string to convert
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
  <warning>
   <para>
    The parameter must be a string.
    Using other data types will produce unexpected results.
   </para>
  </warning>
 </refsect1>
 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   The decimal value of <parameter>binary_string</parameter>
  </para>
 </refsect1>
 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title><function>bindec</function> example</title>
    <programlisting role="php">
<![CDATA[
<?php
echo bindec('110011') . "\n";
echo bindec('000110011') . "\n";

echo bindec('111');
?>
]]>
    </programlisting>
    &example.outputs;
    <screen>
<![CDATA[
51
51
7
]]>
    </screen>
   </example>
  </para>
  <para>
   <example>
    <title><function>bindec</function> interprets input as unsigned integers</title>
    <programlisting role="php">
<![CDATA[
<?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";
}
?>
]]>
    </programlisting>
    &example.outputs.32bit;
    <screen>
<![CDATA[
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
]]>
    </screen>
    &example.outputs.64bit;
    <screen>
<![CDATA[
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
]]>
    </screen>
   </example>
  </para>
 </refsect1>
 <refsect1 role="notes">
  &reftitle.notes;
  <note>
   <para>
    The function can convert numbers that are too large to fit into the platforms
    <type>integer</type> type, larger values are returned as <type>float</type> in
    that case.
   </para>
  </note>
 </refsect1>
 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>decbin</function></member>
    <member><function>octdec</function></member>
    <member><function>hexdec</function></member>
    <member><function>base_convert</function></member>
   </simplelist>
  </para>
 </refsect1>
</refentry>

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