Fastest way to implode an associative array with keys

Question

I\'m looking for a fast way to turn an associative array in to a string. Typical structure would be like a URL query string but with customizable separators so I can use \'<

Answer 1

This is the most basic version I can think of:

public function implode_key($glue = "", $pieces = array())
{
    $keys = array_keys($pieces);
    return implode($glue, $keys);
}