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I have many arrays, each holding instances of Product. Need to get unique products only. From PHP documentation of array_diff:

array array_diff ( array $array1 , array $array2 [, array $... ] )

Two elements are considered equal if and only if (string) $elem1 === (string) $elem2. In words: when the string representation is the same.

Does this mean I'm forced to implement toString() in my instances? Is there any function to compute the difference providing a custom callback?

I didn't tested this code, but I guess it will not work because there is no toString() function in Product:

$categories = array();
// ...

// Unique products from all categories, compared against ===
$uniqueProducts = array();

// Compute unique products
foreach($categories as $category) {
    $uniqueProducts += array_diff($category->getProducts(), $uniqueProducts)
}

return $uniqueProducts;
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2 Answers 2

up vote 1 down vote accepted

Does this mean I'm forced to implement toString() in my instances?

According to the typecast section in the PHP docs manual - you do not need a toString() function. Basically typecasting (string) is the same as if you simply did var_dump($uniqueProducts)

All that the array_diff is doing is typecasting your array.

One option is to make your own "array_diff" function

function my_array_diff($arraya, $arrayb)
{
    foreach ($arraya as $keya => $valuea)
    {
        // Put your own 'test' here - but for example this uses in_array()
        if (in_array($valuea, $arrayb))
        {
            unset($arraya[$keya]);
        }
    }
    return $arraya;
}
share|improve this answer
    
Is typecasting safe for objects? That is, two identical instances will give the same string representation? –  gremo Nov 11 '12 at 11:35
    
tbh - I'm not sure - hence why I included your very own "my_array_diff()" that you can customise how you want to check your objects to look for specific differences/similarities without a typecast –  The Shift Exchange Nov 11 '12 at 11:36
    
I appreciate your answer, but I was looking for a one-line (elegant) way of doing this check. –  gremo Nov 11 '12 at 11:38
    
Well - it is a "one-line" code in your main section - then put "my_array_diff()" somewhere else (maybe in an include file or something) –  The Shift Exchange Nov 11 '12 at 11:45
    
Your only other option is to try something like this: stackoverflow.com/questions/4347293/comparing-arrays-of-objects - but that also uses custom code –  The Shift Exchange Nov 11 '12 at 11:45
up vote 0 down vote

If the product lists are short you could implement your own checking, based on values of your choice?

$uniqueProducts = array();
foreach($productsOne as $productOne) {
  foreach($uniqueProducts as $alreadyListed) {
    if($productOne->getName() != $alreadyListes->getName()) { // You can customise this line to make more specific
      break;
    }
    $uniqueProducts = $productOne; // If product hasn't already been added to the array then it's unique.
  }
}
// Repeat foreaches for second product array, or combine them before teh foreach using $productOne = $productOne+$productTwo.
share|improve this answer
    
Of course I could but I was looking for an elegant solution. Thanks anyways. –  gremo Nov 11 '12 at 11:33

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