<?php
// Log(10, number)

function countLog(& $number){
  try{
    if ($number <= 0){
      throw new Exception("Error. Number should be bigger than 0 \n");
    }
    $number = log10($number);
  }
  catch(Exception $err){
    echo $err->getMessage();
  }
  finally{
    return $number;
  }
}
$number = 0;
echo "Let's count log(10," , $number , ") \n";
$number = countLog($number);
echo "Result is ", $number;