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 st

Answer 1

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 2

PHP allows default arguments (link). In your case, you could define all the parameters from 3 to 8 as NULL or as an empty string "" depending on your function code. In this way, you can call the function only using the first two parameters.

For example:

<?php
  function yourFunction($arg1, $arg2, $arg3=NULL, $arg4=NULL, $arg5=NULL, $arg6=NULL, $arg7=NULL, $arg8=NULL){
echo $arg1;
echo $arg2;
if(isset($arg3)){echo $arg3;}
# other similar statements for $arg4, ...., $arg5
if(isset($arg8)){echo $arg8;}
}

Answer 3

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

Answer 4

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

---

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

Answer 5

NOTE: This is an old answer, for PHP 5.5 and below. PHP 5.6+ supports default arguments

In PHP 5.5 and below, you can achieve this by using one of these 2 methods:

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

How to use

function method_1()
{
  $arg1 = (func_num_args() >= 1)? func_get_arg(0): "default_value_for_arg1";
  $arg2 = (func_num_args() >= 2)? func_get_arg(1): "default_value_for_arg2";
}

function method_2($arg1 = null, $arg2 = null)
{
  $arg1 = $arg1? $arg1: "default_value_for_arg1";
  $arg2 = $arg2? $arg2: "default_value_for_arg2";
}

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

Answer 6

Just set Null to ignore parameters that you don't want to use and then set the parameter needed according to the position.

 function myFunc($p1,$p2,$p3=Null,$p4=Null,$p5=Null,$p6=Null,$p7=Null,$p8=Null){
    for ($i=1; $i<9; $i++){
        $varName = "p$i";
        if (isset($$varName)){
            echo $varName." = ".$$varName."<br>\n";
        }
    }
}   

myFunc( "1", "2", Null, Null, Null, Null, Null, "eight" );