Sort an array by a child array's value in PHP

Question

I have an array composed of arrays. I want to sort the parent array by a property of the child arrays. Here's an example

array(2) {
  [0]=>
  array(3) {
    [0]=>
    string(6) "105945"
    [1]=>
    string(10) "First name"
    [2]=>
    float(0.080878465391)
  }
  [1]=>
  array(3) {
    [0]=>
    string(6) "109145"
    [1]=>
    string(11) "Second name"
    [2]=>
    float(0.0504154818384)
}

I would like to sort the parent array by [2] ascending in the child arrays, so in this case the result would be the child arrays reversed (.05, 08). Is this possible using any of the numerous PHP sort functions?

Answer 1

You can make use of usort function as:

$arr = array(
                array("105945","First name",0.080878465391),
                array("109145","Second name",0.0504154818384)
            );

function cmp($a, $b) {
        if ($a[2] == $b[2]) {
                return 0;
        }
        return ($a[2] < $b[2]) ? -1 : 1;
}

usort($arr,"cmp");

Answer 2

Hi, see this page for example

http://php.net/manual/en/function.sort.php

or example

      <?php 
function multisort($array, $sort_by) {
    foreach ($array as $key => $value) {
        $evalstring = '';
        foreach ($sort_by as $sort_field) {
            $tmp[$sort_field][$key] = $value[$sort_field];
            $evalstring .= '$tmp[\'' . $sort_field . '\'], ';
        }
    }
    $evalstring .= '$array';
    $evalstring = 'array_multisort(' . $evalstring . ');';
    eval($evalstring);

    return $array;
} 

$test = array(
    array( 'a' => '1', 'b' => '3'),
    array( 'a' => '2', 'b' => '1'),
    array( 'a' => '1', 'b' => '1'));

echo 'Unsorted: ';
print_r($test);

$result = multisort( $test , array('a','b') );

echo 'Sorted: ';
print_r($result);
?>

Result:

Unsorted: Array
(
    [0] => Array
        (
            [a] => 1
            [b] => 3
        )

    [1] => Array
        (
            [a] => 2
            [b] => 1
        )

    [2] => Array
        (
            [a] => 1
            [b] => 1
        )

)
Sorted: Array
(
    [0] => Array
        (
            [a] => 1
            [b] => 1
        )

    [1] => Array
        (
            [a] => 1
            [b] => 3
        )

    [2] => Array
        (
            [a] => 2
            [b] => 1
        )

)

Answer 3

I think the following will help u

<?php
$testAry = array(
  array('a' => 1, 'b' => 2, 'c' => 3),
  array('a' => 2, 'b' => 1, 'c' => 3),
  array('a' => 3, 'b' => 2, 'c' => 1),
  array('a' => 1, 'b' => 3, 'c' => 2),
  array('a' => 2, 'b' => 3, 'c' => 1),
  array('a' => 3, 'b' => 1, 'c' => 2)
);

Utility::orderBy($testAry, 'a ASC, b DESC');

//Result:
$testAry = array(
  array('a' => 1, 'b' => 3, 'c' => 2),
  array('a' => 1, 'b' => 2, 'c' => 3),
  array('a' => 2, 'b' => 3, 'c' => 1),
  array('a' => 2, 'b' => 1, 'c' => 3),
  array('a' => 3, 'b' => 2, 'c' => 1),
  array('a' => 3, 'b' => 1, 'c' => 2)
);
?>

To sort an array of objects you would do something like:
Utility::orderBy($objectAry, 'getCreationDate() DESC, getSubOrder() ASC');

This would sort an array of objects that have methods getCreationDate() and getSubOrder().

Here is the function:

<?php
class Utility {
    /*
    * @param array $ary the array we want to sort
    * @param string $clause a string specifying how to sort the array similar to SQL ORDER BY clause
    * @param bool $ascending that default sorts fall back to when no direction is specified
    * @return null
    */
    public static function orderBy(&$ary, $clause, $ascending = true) {
        $clause = str_ireplace('order by', '', $clause);
        $clause = preg_replace('/\s+/', ' ', $clause);
        $keys = explode(',', $clause);
        $dirMap = array('desc' => 1, 'asc' => -1);
        $def = $ascending ? -1 : 1;

        $keyAry = array();
        $dirAry = array();
        foreach($keys as $key) {
            $key = explode(' ', trim($key));
            $keyAry[] = trim($key[0]);
            if(isset($key[1])) {
                $dir = strtolower(trim($key[1]));
                $dirAry[] = $dirMap[$dir] ? $dirMap[$dir] : $def;
            } else {
                $dirAry[] = $def;
            }
        }

        $fnBody = '';
        for($i = count($keyAry) - 1; $i >= 0; $i--) {
            $k = $keyAry[$i];
            $t = $dirAry[$i];
            $f = -1 * $t;
            $aStr = '$a[\''.$k.'\']';
            $bStr = '$b[\''.$k.'\']';
            if(strpos($k, '(') !== false) {
                $aStr = '$a->'.$k;
                $bStr = '$b->'.$k;
            }

            if($fnBody == '') {
                $fnBody .= "if({$aStr} == {$bStr}) { return 0; }\n";
                $fnBody .= "return ({$aStr} < {$bStr}) ? {$t} : {$f};\n";               
            } else {
                $fnBody = "if({$aStr} == {$bStr}) {\n" . $fnBody;
                $fnBody .= "}\n";
                $fnBody .= "return ({$aStr} < {$bStr}) ? {$t} : {$f};\n";
            }
        }

        if($fnBody) {
            $sortFn = create_function('$a,$b', $fnBody);
            usort($ary, $sortFn);       
        }
    }
}
?>