PHP Function with Optional Parameters

Question

I've written a PHP function that can accepts 10 parameters, but only 2 are required. Sometimes, I want to define the eighth parameter, but I don't want to type in empty strings for each of the parameters until I reach the eighth.

One idea I had was to pass an abstracted function with an array of parameters which passes it along to the real function.

Is there a better way to set up the function so I can pass in only the parameters I want?

Answer 1

Note: this is an old post, but can help someone now or in the future.

You can achieve this by using one of this 2 methods:

• using the func_num_args() and func_get_arg() functions;
• using defaults arguments;

How to use

function method_1()
{
  $arg1 = (func_num_args() >= 1)? func_get_arg(0): "default_value_fot_arg1";
  $arg2 = (func_num_args() >= 2)? func_get_arg(1): "default_value_fot_arg2";
}

function method_2($arg1 = null, $arg2 = null)
{
  $arg1 = $arg1? $arg1: "default_value_fot_arg1";
  $arg2 = $arg2? $arg2: "default_value_fot_arg2";
}

I prefer the second method because it's clean and easy to understand, but sometimes you maybe need the first method.

Answer 2

You can just set the default value to null.

<?php
function functionName($value, $value2 = null) {
// do stuff
}

Answer 3

I think, you can use objects as params-transportes, too.

$myParam = new stdClass();
$myParam->optParam2 = 'something';
$myParam->optParam8 = 3;
theFunction($myParam);

function theFunction($fparam){      
  return "I got ".$fparam->optParam8." of ".$fparam->optParam2." received!";
}

Of course, you have to set default values for "optParam8" and "optParam2" in this function, in other case you will get "Notice: Undefined property: stdClass::$optParam2"

If using arrays as function parameters, I like this way to set default values:

function theFunction($fparam){
   $default = array(
      'opt1' => 'nothing',
      'opt2' => 1
   );
   if(is_array($fparam)){
      $fparam = array_merge($default, $fparam);
   }else{
      $fparam = $default;
   }
   //now, the default values are overwritten by these passed by $fparam
   return "I received ".$fparam['opt1']." and ".$fparam['opt2']."!";
}

Answer 4

I know this is an old post, but i was having a problem like the OP and this is what i came up with.

Example of array you could pass. You could re order this if a particular order was required, but for this question this will do what is asked.

$argument_set = array (8 => 'lots', 5 => 'of', 1 => 'data', 2 => 'here');

This is manageable, easy to read and the data extraction points can be added and removed at a moments notice anywhere in coding and still avoid a massive rewrite. I used integer keys to tally with the OP original question but string keys could be used just as easily. In fact for readability I would advise it.

Stick this in an external file for ease

function unknown_number_arguments($argument_set) {

    foreach ($argument_set as $key => $value) {

        # create a switch with all the cases you need. as you loop the array 
        # keys only your submitted $keys values will be found with the switch. 
        switch ($key) {
            case 1:
                # do stuff with $value
                break;
            case 2:
                # do stuff with $value;
                break;
            case 3:
                # key 3 omitted, this wont execute 
                break;
            case 5:
                # do stuff with $value;
                break;
            case 8:
                # do stuff with $value;
                break;
            default:
                # no match from the array, do error logging?
                break;
        }
    }
return;
}

put this at the start if the file.

$argument_set = array(); 

Just use these to assign the next piece of data use numbering/naming according to where the data is coming from.

$argument_set[1][] = $some_variable; 

And finally pass the array

unknown_number_arguments($argument_set);

Answer 5

In PHP 5.6 and later, argument lists may include the ... token to denote that the function accepts a variable number of arguments. The arguments will be passed into the given variable as an array; for example:

Example Using ... to access variable arguments

<?php
function sum(...$numbers) {
    $acc = 0;
    foreach ($numbers as $n) {
        $acc += $n;
    }
    return $acc;
}

echo sum(1, 2, 3, 4);
?>

The above example will output:

10

Variable-length argument lists PHP Documentation

Answer 6

To accomplish what you want, use an array Like Rabbot said (though this can become a pain to document/maintain if used excessively). Or just use the traditional optional args.

//My function with tons of optional params
function my_func($req_a, $req_b, $opt_a = NULL, $opt_b = NULL, $opt_c = NULL)
{
  //Do stuff
}
my_func('Hi', 'World', null, null, 'Red');

However, I usually find that when I start writing a function/method with that many arguments - more often than not it is a code smell, and can be re-factored/abstracted into something much cleaner.

//Specialization of my_func - assuming my_func itself cannot be refactored
function my_color_func($reg_a, $reg_b, $opt = 'Red')
{
  return my_func($reg_a, $reg_b, null, null, $opt);
}
my_color_func('Hi', 'World');
my_color_func('Hello', 'Universe', 'Green');