Taking base_convert past base 36

Code Snippets, Programming No Comments

When building my URL shortener, ZapX, I ran into a bit of a problem. I wanted to be able to make the shortest possible urls using the characters 0-9, a-z, and A-Z, otherwise known as base 62.

PHP’s native base_convert only goes up to base 36, so I was forced to resort to my own devices to get the job done. Long story short, here’s one that goes up to base 62:

function extended_base_convert($dec, $base)
{
 $numchart = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
 $min_base = 2;
 $max_base = strlen($numchart);
 if ($base < $min_base || $base > $max_base)
  return 'N/A';
 $value = $dec;
 $ptr = ceil($value / $base);
 $buf = array();
 do {
  $buf[$ptr] = substr($numchart, ($value % $base), 1);
  $value = intval($value / $base);
  $ptr--;
 } while ($value > 0);
 $buf = array_reverse($buf);
 return implode('', $buf);
}

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