array_multisort with 2d array

[HeidiR]

Hello all,

 

I'm trying to use array_multisort with a 2d array (code below). I have a simple example below which produces the following incorrect results:

 

0) b -> 2

1) a -> 1

2) c -> 3

 

0) 2 -> b

1) 1 -> a

2) c -> 3

 

Note: This example is similar to example #2 on php.net but it doesn't seem to work as advertised. What am I missing???

 

Thanks,

 

HeidiR

 

 

 

<?php

 

$ar[0][0] = "b";

$ar[1][0] = "a";

$ar[2][0] = "c";

$ar[0][1] = "2";

$ar[1][1] = "1";

$ar[2][1] = "3";

 

for($i = 0; $i <= count($ar) -1; $i++) {

echo ($i . ") " . $ar[$i][0] . " -> " . $ar[$i][1] . "<br />");

}

 

echo ("<br />");

 

array_multisort($ar[0], SORT_ASC, SORT_STRING, $ar[1], SORT_ASC, SORT_STRING);

 

for($i = 0; $i <= count($ar) -1; $i++) {

echo ($i . ") " . $ar[$i][0] . " -> " . $ar[$i][1] . "<br />");

}

 

?>

[genericnumber1]

If they're already linked in the array, just use usort() to sort the values you want and the other one will come along for the ride...

 

This should work... (basically copied/pasted from the php manual http://us2.php.net/usort )

function cmp($a, $b)
{
    strcmp($a[0], $b[0]);
}

$ar[0][0] = "b";
$ar[1][0] = "a";
$ar[2][0] = "c";
$ar[0][1] = "2";
$ar[1][1] = "1";
$ar[2][1] = "3";

usort($ar, "cmp");
print_r($ar);

[HeidiR]

If they're already linked in the array, just use usort() to sort the values you want and the other one will come along for the ride...

 

This should work... (basically copied/pasted from the php manual http://us2.php.net/usort )

function cmp($a, $b)
{
    strcmp($a[0], $b[0]);
}

$ar[0][0] = "b";
$ar[1][0] = "a";
$ar[2][0] = "c";
$ar[0][1] = "2";
$ar[1][1] = "1";
$ar[2][1] = "3";

usort($ar, "cmp");
print_r($ar);

 

Thanks for the quick reply and solution. This works great for string arrays.

I have extended your example and created another function to handle sorting a 2d array with numeric values. The usort and _ncmp functions below sort the numeric values correctly.

 

usort($ar, '_ncmp')

 

function _ncmp($a, $b) {

if($a[0] < $b[0]) //col1

return -1;

else

return 1;

}

 

Is there a way to call _ncmp from usort with an argument to dynamically change the sort column? Something like:

 

function _ncmp($a, $b, $sort_col) {

if($sort_col] < $b[$sort_col])

return -1;

else

return 1;

}

[genericnumber1]

it would be easiest to just change the cmp function to

 

<?php
function cmp($a, $b)
{
return strnatcmp($a[0], $b[0]);
}
?>

 

As for passing params to the function called by usort? It might be cleanest if you implement it in a class...

<?php
class OrderedMDArray {
private $array;
private $sortKey;

public function __construct($array, $sortKey) {
	$this->array = $array;
	$this->sortKey = $sortKey;
}

public function get() {
	usort($this->array, array($this, 'cmp'));
	return $this->array;
}

private function cmp($str1, $str2) {
	return strnatcmp($str1[$this->sortKey], $str2[$this->sortKey]);
}
}

$ar[0][0] = "b";
$ar[1][0] = "a";
$ar[2][0] = "c";
$ar[0][1] = "2";
$ar[1][1] = "1";
$ar[2][1] = "3";

$ordArray = new OrderedMDArray($ar, 0);
print_r($ordArray->get());
?>

 

but you can also do it with the global keyword (I hate the global keyword)...

 

<?php
function cmp($a, $b)
{
global $key;
return strnatcmp($a[$key], $b[$key]);
}

$ar[0][0] = "b";
$ar[1][0] = "a";
$ar[2][0] = "c";
$ar[0][1] = "2";
$ar[1][1] = "1";
$ar[2][1] = "3";

$key = 0;
usort($ar, "cmp");
print_r($ar);
?>

 

PS. sorry, forgot the return before the strcmp() in my first reply.

[HeidiR]

it would be easiest to just change the cmp function to

 

<?php
function cmp($a, $b)
{
return strnatcmp($a[0], $b[0]);
}
?>

 

As for passing params to the function called by usort? It might be cleanest if you implement it in a class...

<?php
class OrderedMDArray {
private $array;
private $sortKey;

public function __construct($array, $sortKey) {
	$this->array = $array;
	$this->sortKey = $sortKey;
}

public function get() {
	usort($this->array, array($this, 'cmp'));
	return $this->array;
}

private function cmp($str1, $str2) {
	return strnatcmp($str1[$this->sortKey], $str2[$this->sortKey]);
}
}

$ar[0][0] = "b";
$ar[1][0] = "a";
$ar[2][0] = "c";
$ar[0][1] = "2";
$ar[1][1] = "1";
$ar[2][1] = "3";

$ordArray = new OrderedMDArray($ar, 0);
print_r($ordArray->get());
?>

 

but you can also do it with the global keyword (I hate the global keyword)...

 

<?php
function cmp($a, $b)
{
global $key;
return strnatcmp($a[$key], $b[$key]);
}

$ar[0][0] = "b";
$ar[1][0] = "a";
$ar[2][0] = "c";
$ar[0][1] = "2";
$ar[1][1] = "1";
$ar[2][1] = "3";

$key = 0;
usort($ar, "cmp");
print_r($ar);
?>

 

PS. sorry, forgot the return before the strcmp() in my first reply.

 

 

Thanks for the information. I'll give them a try. 

 

HeidiR