Would it be possible to combine an arrays keys to create a new key using the combined key values?
I'm not asking to create a function to combine them, just wondering if it is possible to do something like this (obviously this code doesn't work, just showing what I meant in code):
<?php
$box = array(
"Width" => 10,
"Height" => 20,
"Total" => ($box["Width"] + $box["Height"]),
);
echo $box["Total"]; // would show up as 30
?>
No, not while the array is being defined. array(...) is being evaluated first, the result of which is assigned = to $box. You can't refer to $box before the evaluation is finished.
You'll have to do it in two steps, or perhaps create a custom class that can do such magic using methods and/or (automagic) getters.
You need 2 steps:
$box = array(
"Width" => 10,
"Height" => 20,
);
$box["Total"] = $box["Width"] + $box["Height"];
echo $box["Total"];
$box would make this answer a little more complete in my eyes.
The easy answer is no.
To elaborate: this is precisely what classes are meant to do. Note that you can do what you are trying to do very simply:
<?php
class Box extends ArrayObject
{
public function offsetGet($key)
{
return $key == 'Total' ? $this['Width'] + $this['Height'] : parent::offsetGet($key);
}
}
$box = new Box(array(
'Width' => 10,
'Height' => 20
));
echo $box['Total'],"\n";
Of course $box is not a true array in this example, and as such, cannot directly be used with array functions. See the docs for ArrayObject.
$w = 10; $h = 20; $total = $w + $h;, but that doesn't mean one shouldn't use arrays. My answer is simply to illustrate a concept: using classes to compute derived values doesn't necessarily involve a lot of code. If you are creating boxes across the entire site, setting up a class to handle them is less error prone because you only have to do it once. In practice, I wouldn't actually use an ArrayObject for this; a standard class would do. And of course if this is just a simple, one time procedure, then I'd do exactly what xdazz has suggested.Since you already have 10 and 20 you can write
<?php
$box = array(
"Width" => 10,
"Height" => 20,
"Total" => 10 + 30,
);
echo $box["Total"]; // would show up as 30
