function log_base ($x, $y)
{
  //variable and initializations
  $the_result = 0.0;
  $temp01     = 0.0;

  //take the base 10 logarithm of y and divide by x
  $temp01 = log10($y) / $x;

  //calculate the result
  $the_result = pow(10.0, $temp01);

  //return the value
  return $the_result;
}

$x = 2.0;
$y = 5.4;

$the_base = log_base ($x, $y);

echo "x = $x<br>";
echo "y = $y<br>";
echo "the_base = $the_base<br>";
?>