What is the best way of reading parameters in functions?

Question

Hi.

I've created several helper functions which I use when creating templates for Wordpress. An example is this:

function the_related_image_scaled($w="150", $h="150", $cropratio="1:1", $alt="", $key="related" )

The problem is, if I only want to pass along the $alt parameter, I also have to populate $w, $h and $cropratio.

In one of my plugins, I use the following code:

function shortcode_display_event($attr) { 
    extract(shortcode_atts(array(
        'type' => 'simple',
        'parent_id' => '',
        'category' => 'Default',
        'count' => '10',
        'link' => ''
    ), $attr));

  $ec->displayCalendarList($data); 
}

This allows me to call the function only using e.g.count=30.

How can I achieve the same thing in my own functions?

SOLUTION
Thanks to my name brother (steven_desu), I have come up with a solution that works.

I added a extra function (which I found on the net) to create value - pair from a string.

The code looks as follows:

// This turns the string 'intro=mini, read_more=false' into a value - pair array
function pairstr2Arr ($str, $separator='=', $delim=',') {
    $elems = explode($delim, $str);
    foreach( $elems as $elem => $val ) {
        $val = trim($val);
        $nameVal[] = explode($separator, $val);
        $arr[trim(strtolower($nameVal[$elem][0]))] = trim($nameVal[$elem][1]);
    }
        return $arr;
}

function some_name($attr) {
  $attr = pairstr2Arr($attr);

  $result = array_merge(array(
        'intro' => 'main',
        'num_words' => '20',
        'read_more' => 'true',
        'link_text' => __('Read more')
    ), $attr);

  extract($result);

  // $intro will no longer contain'main' but will contain 'mini'
  echo $intro;
}

some_name('intro=mini, read_more=false')

Info
With good feedback from Pekka, I googled and found some info regarding the Named Arguments and why it's not in PHP: http://www.seoegghead.com/software/php-parameter-skipping-and-named-parameters.seo

Answer 1

New Answer:

Could you not write the function using the extract function's default EXTR_OVERWRITE option?

function the_related_image_scaled($params) {
    $w="150"; $h="150"; $cropratio="1:1"; $alt=""; $key="related";
    extract($params);
    //Do Stuff
}

Called with:

the_Related_image_scaled(array("alt"=>"Alt Text"));

---

You have the option of defaulting the parameters to null and only using them if they are not null:

function the_related_image_scaled($w=null, $h=null, $cropratio=null, $alt=null, $key = null) {
    $output = //Get the base of the image tag
              //including src leave a trailing space and don't close
    if($w!==null) {
        $output .= "width=\"$w\"";
    }
    //... Through all your parameters
    return $output;
}

So only passing the alt parameter would look like:

echo the_related_image_scaled(null,null,null,$alt);

Answer 2

I would suggest using array_merge() and extract() at the beginning of your function, then passing parameters as arrays if this is a possibility.

function whatever($new_values){
    $result = array_merge(array(
        "var1" => "value1",
        "var2" => "value2",
        "var3" => "value3"
    ), $new_values);
    extract($result);

    echo "$var1, $var2, $var3";
}

whatever(array("var2"=>"new_value"));

The above will output:

value1, new_value, value3

it's a bit sloppy and uses more memory since it has to allocate the arrays, so it's the less efficient solution. But it does allow you to avoid redundancy. I'm sure a better method exists using magic meta-code, but I can't think of it off-hand.

Answer 3

Say this is your function:

function related_image_scaled($w="150", $h="150", $alt="", $key="related")

You can do this:

class ImageScaleParams {
    public $w = 150;
    public $h = 150;
    public $cropratio = "1:1";
    public $alt = "";
    public $key = "related";
}

function related_image_scaled(ImageScaleParams $params) { ... }

Then call it like this:

$imgscale = new ImageScaleParams();
$imgscale.alt="New Alt";
related_image_scaled($imgscale);

You can also have various factories in ImageScaleParams such as:

class ImageScaleParams {
    static function altFactory($alt) {
        $imgscale = new ImageScaleParams();
        $imgscale->alt = $alt;
        return $imgscale;
    }
}

Which you could call like this (equivalent to previous example):

related_image_scaled(ImageScaleParams::altFactory("New Alt"));