Extract a section of an array into a new array?

[jasonla]

Hi. I'm trying to extract a range of indexes from an array in a specific manner.

If my array is:

$articleList = array (
    array('article_id' => '1',
        'category_id' => '1',
        'article_text' => 'arbitary text'),

array('article_id' => '2',
     'category_id' => '1',
     'article_text' => 'arbitary text'),

array('article_id' => '3',
     'category_id' => '2',
     'article_text' => 'arbitary text'),

array('article_id' => '4',
     'category_id' => '2',
     'article_text' => 'arbitary text'),

array('article_id' => '5',
     'category_id' => '2',
     'article_text' => 'arbitary text'),

array('article_id' => '6',
     'category_id' => '3',
     'article_text' => 'arbitary text'),

array('article_id' =>' 7',
     'category_id' => '3',
     'article_text' => 'arbitary text'),

array('article_id' => '8',
     'category_id' => '4',
     'article_text' => 'arbitary text')
);

The first value is a primary key for the article, the second value is the primary key of the category the article belongs to. I want to extract the articles into a new array for each category, meaning a new array would be created to hold only articles from category 1, a new array with only category 2 articles, etc, etc.

Constraint: The number of articles per category varies.

Can anyone think of a way to achieve this? Is there a built-in PHP function that does it? I'd rather use a built-in function because of its speed.

Any help is very much appreciated, thank you.

[Installer]

It ain't pretty and it ain't built-in, but here's one way to do it:

foreach ($articleList as $key => $val) {
    ${'category_' . $val['category_id']}[] = array('article_id' => $val['article_id'], 'article_text' => $val['article_text']);
}

[jasonla]

Hehe. I came up with basically the same thing, Installer. Thank you for the input, though. I was hoping somoene would know of a more efficient way to do this.

[Installer]

You're welcome. Wasting time is why I'm here.