PHP gets a collection of a certain key in a two-dimensional array

This article is for code sharing. I saw some "big cow" code at work and wanted to share it.

This is specifically, the following two-dimensional array is read from the library.

Code List:

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1. $user = array(
2. 0 => array(
''Id' = & gt; 1,
3. E'Name '= & gt; ' Zhang San ',
4. I'email '= & gt; 'zhangsan@sina.com',
5. ), 1 => array(
''Id' = & gt; 2,
7.                                                                                                                                                                                                                         'name'       => " ),
2 =>
8. array( ''Id' = & gt; 5,
9. E'Name '= & gt; ' king five ',
                                                                                                                                                                                                                       with 'email' =>
10. ),  …  );
12. The above array format is mainly familiar to everyone who has played with PHP+MYSQL.
13. So, now there are two requirements:
14. 1) Get the collection of index "id" and save it as a one-bit array, that is, get array(1,2,5) I don’t know how my friends would write it?
15. If it were the way I wrote it in the past, I would directly use foreach, and then use array_push to stuff into array variables one by one. This can also be achieved. But this way of writing affects performance, because using PHP's native functions is definitely more efficient than looping. Code List:
17. [php]
18. view plain

copy

$ids =

array();

$ids = array_map('array_shift', $user);

The above code can get the results we want. Please refer to the manual for the use of functions.

In fact, there is another solution here, using the array_column function, but this function requires PHP version requirements, (PHP 5 >= 5.5.0)

Code List:

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1. $ids = array();
2. $ids = array_column($user, 'id');

In this case, the efficiency will definitely be higher.

2)Get the set of index "name" and save it as a one-bit array, that is, get array('Zhang San','Li Si','Wang Wu')

According to my previous writing method, it is still the same foreach, and then array_push is inserted into an array variable one by one. See the efficient code listing.

Code List:

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1. $names = array();
2. $names = array_reduce($user, create_function('$v,$w', '$v[$w["id"]]=$w["name"];return $v;' ));

Get the result:

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1. array(
2. 1 => 'Zhang San',
3. 2 => '李思',
4. 5 => '王五',
5. );

Children's shoes that are often foreached, please correct them as soon as possible!

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