How to work around with php functions

function.php

<?php

function function_name($parameters, $param2, $para3 = ""){
    // what you want to do with the parameters entered
    if(strlen($para1 !== 0)){
       echo "Has ".$para1." Characters";
    }
   // the third parameter is option you can choose to supply
   // the value or leave it
   // The other parameters can be defined in anyway that suites you

}


?>