Sorting Multi Dimensional Arrays

tguill

This is my Mulit-Dim array:

Array (
[0] => Array ( [latitude] => 28.066284 [longitude] => -82.216304 [dist] => 16.8467090256 )
[1] => Array ( [latitude] => 28.068117 [longitude] => -82.299313 [dist] => 14.7736745307 )
[2] => Array ( [latitude] => 27.938454 [longitude] => -81.990367 [dist] => 23.7279350068 )
[3] => Array ( [latitude] => 27.843002 [longitude] => -82.728622 [dist] => 21.9764064392 )
[4] => Array ( [latitude] => 28.157392 [longitude] => -82.015702 [dist] => 29.6361789323 )
)

I'd like to sort this by the [dist] column. How do I do this using the PHP sort commands? I've been trying the array_multisort() command, but I can't seem to get it.

Thanks!

laserlight

You can use [man]usort/man.

Weedpacket

You could use [man]usort[/man] and write a function that compares the 'dist' part of two arrays.

tguill

Weedpacket wrote:
You could use [man]usort[/man] and write a function that compares the 'dist' part of two arrays.

Great! That works smooth except one thing ...it's sorting based on string value and not a numerical value so I'm getting:

22
23.4
31
40.4
8.1

instead of:

8.1
22
23.4
31
40.4

How do I fix this? I tried plugging in floatval() like this:

function cmp_dist($a, $b)
{
   return strcmp(floatval($a["dist"]), floatval($b["dist"]));
}

But that didn't work. Any ideas?

Thanks!

Installer

foreach ($array as $key => $value) {
    $tmp[] = $value['dist'];
}
array_multisort($tmp, SORT_NUMERIC, $array);

Weedpacket

Installer wrote:
[what he said]

That's the bit I always disliked about array_multisort - the need for a temporary array.

tguill wrote:
return strcmp(floatval($a["dist"]), floatval($b["dist"]));

Well if they're floats then you wouldn't want to use a string comparison any more, would you? You just need their difference.

Installer

...the need for a temporary array.

That's a good point, although with "usort()" you need two effectively temporary variables, repeated n times.

Weedpacket

Yeah, but they're only single pointers to existing elements, and they're gone by the end of the call. It's not a matter of constructing an entire array that is left hanging around later.

alpha_juno

Installer wrote:

foreach ($array as $key => $value) {
    $tmp[] = $value['dist'];
}
array_multisort($tmp, SORT_NUMERIC, $array);

Thanks for this ;]

laserlight

You resurrected a thread that was dormant for well over a year, but a solution to tguill's problem that uses usort() is:

usort($array, create_function('$a, $b', 'return $a["dist"] - $b["dist"];'));