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

Make the function take one parameter: an array. Pass in the actual parameters as values in the array.

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Edit: the link in Pekka's comment just about sums it up.

Answer 2

What I have done in this case is pass an array, where the key is the parameter name, and the value is the value.

$optional = array(
  "param" => $param1,
  "param2" => $param2
);

function func($required, $requiredTwo, $optional) {
  if(isset($optional["param2"])) {
    doWork();
  }
}

Answer 3

Check default argument values on the php documentation.

Answer 4

func( "1", "2", default, default, default, default, default, "eight" );

Answer 5

If you are commonly just passing in the 8th value, you can reorder your parameters so it is first. You only need to specify parameters up until the last one you want to set.

If you are using different values, you have 2 options.

One would be to create a set of wrapper functions that take different parameters and set the defaults on the others. This is useful if you only use a few combinations, but can get very messy quickly.

The other option is to pass an array where the keys are the names of the parameters. You can then just check if there is a value in the array with a key, and if not use the default. But again, this can get messy and add a lot of extra code if you have a lot of parameters.

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');

Answer 7

If only two values are required to create the object with a valid state, you could simply remove all the other optional arguments and provide setters for them (unless you dont want them to changed at runtime). Then just instantiate the object with the two required arguments and set the others as needed through the setter.

Further reading

• Martin Fowler on Constructor vs Setter Injection and
• Dependency injection through constructors or property setters?