如何按元素长度将PHP数组分组？

Question

I have an array like:-

array("a","b","ab","xy","abc","xyz","abcd","abcde");

I want to group this array by value's length. So it should be like:-

  array(
    "1" => array("a","b"), //because there are two value which their lengths are = 1
    "2" => array("ab","xy"),
    "3" => array("abc","xyz"),
    "4" => array("abcd"),
    "5" => array("abcde")
  );

Than I want to reverse order by index;

Final output should;

array(
  "13" => array("13 length char"),
  "12" => array("12 length char"),
  ...
  ...
  "5" => array("abcde"),
  "4" => array("abcd"),
  "3" => array("abc","xyz"),
  "2" => array("ab","xy"),
  "1" => array("a","b")
);

After I used krsort() output is

Array(
[10] => Array
    (
        [0] => Abdülbari
    )

[8] => Array
    (
        [0] => ablefari
    )

[7] => Array
    (
        [0] => arakari
    )

[3] => Array
    (
        [0] => ari
    )

[14] => Array
    (
        [0] => ağari beğari
    )

[20] => Array
    (
        [0] => ağır erkeli muzari
    )

[12] => Array
    (
        [0] => Amerikanvari
        [1] => amudufıkari
    )

[5] => Array
    (
        [0] => abari
        [1] => abari
        [2] => Acari
        [3] => apari
        [4] => atari
    )

[6] => Array
    (
        [0] => abbari
        [1] => antari
        [2] => asgari
        [3] => asgari
        [4] => aşari
    )

 )

Array index should ordered from bigger index to lower index like: 20,14,12..

Answer 1

You can do this, quite easily, with a combination of mb_strlen() , foreach() loop, and a temporary array in which you use the length as the key.

Now, I'm not going to write out the code for you, as this strikes me very similar to a homework/test project. But if you take a look at the following links, they should help you get started:

http://php.net/manual/en/function.mb-strlen.php
http://php.net/manual/en/control-structures.foreach.php

Edit, added:

Seeing as there have been a couple of answers already posting the code, I don't see any further harm coming from posting one myself.

/**
 * Groups the values based upon their length, and returns
 * an array sorted by descending order of length.
 * 
 * Note: This expects the values to be encoded with UTF-8.
 * 
 * @param array $array
 * @return array
 */
function group_values ($array) {
    // Create the temp variable to hold the sorted values.
    $tmp = array ();

    foreach ($array as $elm) {
        // First we need the length of the string, to use as the index for the grouping.
        $len = mb_strlen ($elm, 'UTF-8');

        // Add the element to the temp array, as a new element for the index key.
        $tmp[$len][] = $elm;
    }

    // Sort the array in reverse order, forcing a numerically comparison.
    krsort ($tmp, SORT_NUMERIC);

    // Return the finished array.
    return $tmp;
}

Answer 2

Or maybe just walk the array with a function that checks the length of a given value and assigns it to a group.

<?php
    $arr = [ 'a','b','ab','xy','abc','xyz','abcd','abcde' ];
    $groups = [];

    array_walk( $arr, function( &$value, $key ) use (&$groups) {
        $groups[ mb_strlen( $value ) ][] = $value;
    });
?>

You can see the running example https://eval.in/671158

Note you need at least PHP 5.3 to be able to inherit scope, with use keyword.

Also, there's no point in reversing the array. When you iterate as follows:

$count = count( $groups );
for ( $i = $count; $i >= 0; --$i )
    print_r( $groups[ $count - $i ] );

And you are printing them as ordered as well. Again, no need to abuse php functions just because they seem easier to write in.

Answer 3

You can do it like below:-

<?php

$array = array("a","b","ab","xy","abc","xyz","abcd","abcde");

$final_array = array();
foreach ($array as $arr){
   $final_array[strlen( $arr)][] =  $arr;  //I have checked the  length of values and make it the key so that automatically your each value will go to corresponding length array
}

echo "<pre/>";print_r($final_array);

Output:- https://eval.in/671126

Note:- I have checked the length of values and make it the key so that automatically your each value will go to corresponding length array

final output what you want:- https://eval.in/671137