Implode column of private values from an array of objects

Question

I have an array of objects and I want to implode a specific private property from each object to form a delimited string.

I am only interested on one of the properties of that array. I know how to iterate the data set via foreach() but is there a functional-style approach?

$ids = "";
foreach ($itemList as $item) {
    $ids = $ids.$item->getId() . ",";
}
// $ids = "1,2,3,4"; <- this already returns the correct result

My class is like this:

class Item {
    private $id;
    private $name;

    function __construct($id, $name) {
        $this->id=$id;
        $this->name=$name;
    }
    
    //function getters.....
}

Sample data:

$itemList = [
    new Item(1, "Item 1"),
    new Item(2, "Item 2"),
    new Item(3, "Item 3"),
    new Item(4, "Item 4")
];

Do you actually need "cheaper", as opposed to clear, obvious code? If not, just go for the loop. — Ken
– Ken, Commented Aug 20, 2014 at 16:26
Probably the most expensive resource is you, and future maintainers. Keep the code as simple and readable as possible, and if you find you need to optimise you can always come back when you've benchmarked and pinpointed the problem areas. — Ken
– Ken, Commented Aug 21, 2014 at 14:43

Staves · Accepted Answer · 2023-10-10 21:12:12Z

6

Use array_map before you implode:

$ids = implode(",", array_map(function ($item) {
    return $item->getId();
}, $itemList));

edited Oct 10, 2023 at 21:12

Staves

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answered Aug 20, 2014 at 16:23

Halcyon

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Comments

mickmackusa · Accepted Answer · 2023-10-10 22:41:17Z

You've "yatta-yatta"ed your getter scripting, so I'll demonstrate two functional style approaches for two getter approaches.

If the class contains an explicitly named method: (Demo)

public function getId()
{
    return $this->id;
}

then you can use 2 cycles:

echo implode(',', array_map(fn($obj) => $obj->getId(), $itemList));

or 1 cycle with a conditional:

echo array_reduce(
         $itemList,
         fn($result, $obj) => $result . ($result ? ',' : '') . $obj->getId()
     );

If the class contains the magic method __get(): (Demo)

public function __get($prop)
{
    return $this->$prop;
}

then you can use 2 cycles:

echo implode(',', array_map(fn($obj) => $obj->id, $itemList));

or 1 cycle with a conditional:

echo array_reduce(
         $itemList,
         fn($result, $obj) => $result . ($result ? ',' : '') . $obj->id
     );

Michael Wagner · Accepted Answer · 2014-08-20 16:22:45Z

-3

You can simply use $ids = implode(',',$itemList);

answered Aug 20, 2014 at 16:22

Michael Wagner

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1 Comment

Paullo Over a year ago

That is if the __toString returns $id. The __toString return a different thing

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