Calling functions with multiple arguments in php

Question

I have defined a php function:

function my_function($text = '', $relative = false, $icon = true) {
//do something
}

It works as expected with default values. But when I want to change the value of one variable it doesn't work:

my_function($icon = false); // this doesn't change anything

I have to call it with all variables to make changes take effect:

my_function($text = '', $relative = false, $icon = false); // this changes the output

I am working in php 5.4.1 and Wordpress. What I do wrong? Thanks.

don't use the formal parameter names inside the parameter parts when "using" that function. so e.g. its "my_function(false)" in the first example. — Hajo
– Hajo, Commented May 2, 2012 at 20:48
That was proposed as a php feature a long time ago. It never made it in though. I liked the idea, although I cant say I'd use it all that often. — goat
– goat, Commented May 2, 2012 at 23:34

Mark · Accepted Answer · 2012-05-02 21:16:21Z

3

You must provide values for any default arguments to the left (in function signature) of the argument you want to change.

So given the function:

function my_function($text = '', $relative = false, $icon = true) {
//do something
}

Here are some examples:

// $text = "foo", $relative = false, $icon = true
my_function("foo"); 

// $text = "", $relative = true, $icon = true
my_function("", true) 

// $text = "", $relative = false, $icon = false
my_function("", false, false)

answered May 2, 2012 at 21:16

Mark

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Comments

gen_Eric · Accepted Answer · 2012-05-02 21:02:11Z

2

my_function($icon = false);

You can't do that in PHP. Well, you can, but it doesn't do what you think it does. What this does is:

Sets $icon to false
Passes false as the 1st parameter to my_function

If you want to change the third parameter, you need to also pass the first two.

my_function('', false, true);

Note: I think it's python that lets you call functions like that, to set only the Xth parameter.

answered May 2, 2012 at 21:02

gen_Eric

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4 Comments

halfer Over a year ago

I frequently use this syntax in PHP, but yes, it doesn't let one skip the previous parameters. I tend to use the old-style 'private' naming convention to indicate it shouldn't be reused: my_function($_icon = false);.

gen_Eric Over a year ago

What do you mean by "old-style 'local' naming convention"? How does that indicate "it shouldn't be reused"?

halfer Over a year ago

It won't stop its reuse, of course. But its prefix is enough for me to know I won't use it elsewhere as a proper variable in the current scope.

halfer Over a year ago

Old style 'local' - my mistake, I meant 'private' (fixed). Prior to PHP getting a specific mechanism for class attribute visibility, the convention was (iirc) to use an underscore prefix for private variables.

Shomz · Accepted Answer · 2012-05-02 20:50:19Z

1

Nothing wrong, that's how PHP works. And when you're calling a function, you shouldn't put variables in the parameter list as you might get undesired results as the variables will be assigned those values. So, this is fine:

my_function('', false, false);

or:

my_function($text, $relative, $icon);

or anything in between, no need to assign values.

answered May 2, 2012 at 20:50

Shomz

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Comments

Fazle Elahee · Accepted Answer · 2012-05-02 21:12:17Z

1

You may use below code:

<?php

function my_function($arg = array("text"=>'Default',"relative"=>false,"icon"=>false))
{
  extract($arg);
      $text = isset($text)?$text:"";
      $relative = isset($relative)? $relative : false;
      $icon = isset($icon)? $icon : false;

      //do something

}

my_function(array("icon"=>true));

?>

WARNING: if you use this way. you should initialise the variable or check the if it is exists.

answered May 2, 2012 at 21:12

Fazle Elahee

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