按对象属性分组php对象数组

Question

I have a php object (book) with 3 properties: name, category, description I then have a list of these book objects in an array. I want to create a new associative array for these objects grouped by category .

Say I have 4 book objects in an array called $books

name    category  description
==================================
book1   cat1     this is book 1
book2   cat1     this is book 2
book3   cat2     this is book 3
book4   cat3     this is book 4

how can I create an associative array called $categories

$categories['cat1'] = array(book1, book2)
$categories['cat2'] = array(book2)
$categories['cat3'] = array(book3)

where book? is the book object and not the word

Answer 1

Like this:

foreach($books as $book)
{ 
    $categories[$book->category][] = $book;
}

Answer 2

You can do it with ouzo goodies :

 $categories = Arrays::groupBy($books, Functions::extractField('category'));

See: http://ouzo.readthedocs.org/en/latest/utils/arrays.html#groupby

Answer 3

Simply loop the array of objects into a new array with the key being the category:

$newArray = array();
foreach($array as $entity)
{
    if(!isset($newArray[$entity->category]))
    {
         $newArray[$entity->category] = array();
    }

    $newArray[$entity->category][] = $entity;
}

Is this what you was looking for ?

Explanation of the code:

/*
    * Create a new blank array, to store the organized data in.
*/
$newArray = array();

/*
    * Start looping your original dataset
*/
foreach($array as $entity)
{

    /*
        * If the key in the new array does not exists, set it to a blank array.
    */
    if(!isset($newArray[$entity->category]))
    {
         $newArray[$entity->category] = array();
    }

    /*
        * Add a new item to the array, making shore it falls into the correct category / key
    */
    $newArray[$entity->category][] = $entity;
}

Answer 4

I had a similar problem, but a bit more complicated with wordpress and metavalues/metakeys (where $results was an array of associative arrays fetched from a $wpdb->get_results() query.

This was my solution adapted to your problem:

$categories = array();
foreach ($results as $row) {
    $id =  $row['category'];
    $description = $row['category'];
    $name = $row['name']
    if (!isset($categories[$id])) {
        $categories[$id] = array();
    }
    $categories[$id] = array_merge($categories[$id], 'description'=>$description , 'name'=>$name);
}

Then you can run another for loop to get each array from the categories array:

foreach ($categories as $category) {
    var_dump($category);
}

Answer 5

如果要通过从具有或不具有其他参数的特定方法获取键来对对象进行分组，则可以使用此库方法：

Arr::groupObjects(array $objects, string $method, ...$args): array

Answer 6

$categories = array();

for ($i = 0; $i < count($books); $i++){
    if (isset($categories[$books[$i]->category]) == false)
        $categories[$books[$i]->category] = array();

    $categories[$books[$i]->category][] = $books[$i]
}

cheers

Answer 7

Try this:

$categories = array();
foreach ($books as $book){

  if (!array_key_exists($book->category , $categories))
     $categories[$book->category] = array();

  $categories[$book->category][] = $book;

}

Answer 8

This should works:

$categories = array();
foreach ($books as $book) {

    $categories[$book['category']][] = $book;

}