Php multi-dimensional array sorting method-PHP source code

This article describes in detail how to sort multi-dimensional arrays. The array_multisort () function can sort multiple PHP arrays, the sorting result is that all arrays are arranged in the order of the first array. It's a bit of a sticky interface, and I'm sure you don't understand it either way. This article describes in detail how to sort multi-dimensional arrays. The array_multisort () function can sort multiple PHP arrays, the sorting result is that all arrays are arranged in the order of the first array. It's a bit of a sticky interface, and I'm sure you don't understand it either way.

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Here is an example:

For example, array_multisort ($ a, $ B), $ a, and $ B are two arrays. After sorting, the 3rd elements in the $ a array are ranked first, then, the third element of $ B is ranked first regardless of its size in $ B. Check the program running result below:

The Code is as follows:
$ A = array (100,80, 50,10, 0 ); $ B = array ("c", "f", "q", "e", "z "); Array_multisort ($ a, $ B ); Var_dump ($ ); Var_dump ($ B ); ?> Running result: Array (5) {[0] => int (0) [1] => int (10) [2] => int (50) [3] = & gt; int (80) [4] = & gt; int (100 )} Array (5) {[0] => string (1) "z" [1] => string (1) "e" [2] => string (1) "q" [3] => string (1) "f" [4] => string (1) "c "}

Obviously, the z of the fifth element of array B is ranked first!

In fact, it turns out that array_multisort () First sorts the first array by the size of the key value, then the other arrays are adjusted according to the adjustment policy of the first array -- put the third element in the first place, and put the second element in the second place ...... -- In fact, the most basic embodiment of this multi-dimensional array Sorting Algorithm!

Note that the number of elements in the two arrays must be the same. Otherwise, a warning message is displayed:
Warning: array_multisort () [function. array-multisort]: Array sizes are inconsistent in ......

Well, I hope you can use the above. Let's talk about the main thing: array_multisort () sorts multi-dimensional arrays. This function will be very useful for future projects!

First, let's take a look at the operation method for sorting each element of the multi-dimensional array [array], which is very simple, but there are several parameters to describe, if you have some knowledge about SQL, you will understand it at a Glance:

The Code is as follows:
// Let's construct a multi-dimensional array $ A = array (, 2, 7 ); $ B = array ('AB', 'ac', 'ad', 'ag', 'ap '); $ AB = array ($ a, $ B ); // Start sorting Array_multisort ($ AB [0], SORT_NUMERIC, SORT_DESC, $ AB [1], SORT_STRING, SORT_ASC ); Print_r ($ AB ); ?>

Note: First, we use SORT_NUMERIC to declare that the $ AB [0] is sorted by numerical type, and SORT_DESC is used.
The declared order is in reverse order (from large to small), and then we sort $ AB [1] In string type. The order is in ascending order (order)
The sorting result of the last array $ AB is a combination of the two. First, sort the result in the reverse order of $ AB [0, if $ AB [0] contains values of the same size, the values are arranged in the order of $ AB [1]. The output result is as follows:

The Code is as follows:
Array ( [0] => Array ([0] => 100 [1] => 7 [2] => 7 [3] => 4 [4] => 2) [1] => Array ([0] => AB [1] => ag [2] => ap [3] => ad [4] => ac) )

Is it similar to using order by in a database? Actually, it's almost the same!

Now let's look at a more practical example:

The Code is as follows:

$ Array [] = array ("age" => 20, "name" => "li "); $ Array [] = array ("age" => 21, "name" => "ai "); $ Array [] = array ("age" => 20, "name" => "ci "); $ Array [] = array ("age" => 22, "name" => "di "); Foreach ($ array as $ key => $ value ){ $ Age [$ key] = $ value ['age']; $ Name [$ key] = $ value ['name']; } Array_multisort ($ age, SORT_NUMERIC, SORT_DESC, $ name, SORT_STRING, SORT_ASC, $ array ); Print_r ($ array ); ?>

In this example, the $ array [] array is constructed based on the records read from the database. We now arrange them in the order of age, if they are of the same age, they are sorted by names. This sort will be frequently used in the future,
Because the sorting parameter required by array_multisort () must be a column, we use foreach to read the age and name of this array. after that?
As in the preceding example, sort the array. the last $ array parameter must be sorted, because the two front parameters have no relationship with the PHP array to be sorted in form, although they are actually the data in $ array -- the columns we extract from $ array -- sorting of course requires columns, we haven't seen sorting with row data yet!

The output result is as follows:

The Code is as follows:
Array ( [0] => Array ([age] => 22 [name] => di) [1] => Array ([age] => 21 [name] => ai) [2] => Array ([age] => 20 [name] => ci) [3] => Array ([age] => 20 [name] => li) )

As you can see, it's actually quite simple, that is, the several parameters that need to be capitalized are a little annoying! Although it is a bit difficult to understand, but it is good to understand, it will be very useful in the future!
Appendix:
Sort order mark:

SORT_ASC-sort by Ascending Order
SORT_DESC-sort by descent

Sorting type flag:

SORT_REGULAR-compare projects by common methods
SORT_NUMERIC-compare projects by numerical values
SORT_STRING-compare items by string

You cannot specify two sorting flags of the same type after each array. The sorting flag specified after each array is only valid for this array-the default values are SORT_ASC and SORT_REGULAR.