php将任意进制数转换成10进制的方法

<?php

# Show the steps involved in converting a number

# from any base (like octal or hex) to base 10

# See below for examples, instructions and copyright

function show_convert_to_base_10 ($number, $base)

{

 // If the number contains a decimal component

 if (strstr ($number, '.'))

 {

  // Get the integer and decimal components

  list ($integer, $decimal) = explode ('.', $number);

 }

 else

 {

  // The number is an integer

  $integer = $number;

 }

  print "<b>Convert the base $base number $number to a

  base 10 number:</b><blockquote>";

  print "Convert the integer component ($integer) of the

   number:";

 // Compute the value of the integer component

 // Loop through the integer digit by digit

 // Reverse the number for easier handling

 $integer = strrev ($integer);

 $length = strlen ($integer);

 for ($pos = 0; $pos </blockquote>';

 if (isset ($decimal))

 {

   print "Convert the decimal component (0.$decimal)

   of the number:<blockquote>";

  // Pad the number with a leading 0 so that we can

  // start at position 1

  $decimal = '0'.$decimal;

  $length = strlen ($decimal);

   for ($pos = 1; $pos < $length; ++$pos) {

   $digit = $decimal[$pos];

   // Handle character values for digits

   // (for bases greater than 10)

   if (eregi ('[a-z]', $digit))

   {

     $digit_value =

     (ord (strtolower ($digit))

     - ord ('a')) + 10;

      $digit = "$digit ($digit_value)";

   }

   else

   {

     $digit_value = $digit;

   }

   // Multiply the current digit by the radix

   // raised to the power of the current position

   $result = $digit_value * pow (1/$base, $pos);

    print "Multiply the value of the digit at

    position $pos by the value of the 1/radix

    ($base) raised to the power of the position

    ($pos):<br/>";

    print "$digit * 1/$base<sup>$pos</sup> =

    $result<br/><br/>";

    $sums[] = $result;

  }

  print '</blockquote>';

 }

 $sums = implode (' + ', $sums);

 eval ("\$base_10_value = $sums;");

  print "</blockquote>The value of the base $base number

  $number in base 10 is $base_10_value. <br/>";

  print "This number is derived from the sum of the values

  of the previous operations ($sums). <br/> <br/>";

}