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

User · Answer

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    lt  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

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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

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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 lt 9   i              varName    quot p i quot           if  isset   varName                echo  varName  quot     quot    varName  quot  lt br gt  n quot                         myFunc   quot 1 quot    quot 2 quot   Null  Null  Null  Null  Null   quot eight quot

User · Answer

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

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I think  you can use objects as params-transportes  too    myParam   new stdClass     myParam- gt optParam2    something    myParam- gt optParam8   3  theFunction  myParam    function theFunction  fparam           return  I got    fparam- gt optParam8   of    fparam- gt 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    gt   nothing          opt2    gt  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

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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   lt  php function sum     numbers         acc   0      foreach   numbers as  n             acc     n            return  acc     echo sum 1  2  3  4     gt    The above example will output   10   Variable-length argument lists PHP Documentation

User · Answer

func   1    2   default  default  default  default  default   eight

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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   gt   lots   5   gt   of   1   gt   data   2   gt   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   gt   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

User · Answer

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    gt   1   func get arg 0    quot default value for arg1 quot      arg2    func num args    gt   2   func get arg 1    quot default value for arg2 quot      function method 2  arg1   null   arg2   null       arg1    arg1   arg1   quot default value for arg1 quot      arg2    arg2   arg2   quot default value for arg2 quot      I prefer the second method because it s clean and easy to understand  but sometimes you may need the first method

User · Answer

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    gt   param1     param2    gt   param2     function func  required   requiredTwo   optional      if isset  optional  param2           doWork

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function yourFunction  var1   var2   optional   Null          code     You can make a regular function and then add your optional variables by giving them a default Null value   A Null is still a value  if you don t call the function with a value for that variable  it won t be empty so no error

User · Answer

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

User · Answer

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

User · Answer

You can just set the default value to null    lt  php function functionName  value   value2   null       do stuff

[php] PHP Function with Optional Parameters

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