php - sort and delete duplicates in a multidimensional array?

[c41122ino]

Trying to sort an array by zip, then by distance, and then filter out any duplicates. Right now, my code just yields:

Warning: usort() [function.usort]: Invalid comparison function

I'm not sure, but I suspect that since this whole thing is in a class, I can't call it the way I'm currently doing?

Anyway, I've got an array that looks like this:

Array
(
    [0] => Array
        (
            [zip] => '01505'
            [distance] => '7.8405015332347'
            [tpid] => 32112                                             

        )

[1] => Array
    (
        [zip] => '01505'
        [distance] => '6.50172229325415'
        [tpid] => 32112                                             
    )

[2] => Array
    (
        [zip] => '01505'
        [distance] => '4.50967688350022'
        [tpid] => 43444                                             
    )

[3] => Array
    (
        [zip] => '01564'
        [distance] => '6.91151548994925'
        [tpid] => 32112                                             
    )

[4] => Array
    (
        [zip] => '02021'
        [distance] => '6.52192787895371'
        [tpid] => 43444                                             
    )

[5] => Array
    (
        [zip] => '02021'
        [distance] => '6.91070971397532'
        [tpid] => 32112                                             
    )
)

First, I'm trying to sort them by zip and second, I'm trying to delete the array element if it's a duplicate and whose distance value is higher than the other one.

So, based on the example above, I'm trying to create:

Array
(
    [0] => Array
        (
            [zip] => '01505'
            [distance] => '4.50967688350022'
            [tpid] => 43444                                             

        )

[1] => Array
    (
        [zip] => '01564'
        [distance] => '6.91151548994925'
        [tpid] => 32112                                             
    )

[2] => Array
    (
        [zip] => '02021'
        [distance] => '6.52192787895371'
        [tpid] => 43444                                             
    )
)

This is all within a class. So, I have this:

class DatabaseConnect {

    function DatabaseConnect() {
            $this->connection = pg_connect(DB_HOST . ' '. PORT . ' ' . DB_NAME . ' '. DB_USER . ' '. DB_PASS);
    }

   function cmp($a, $b) {

            if ($a['zip'] == $b['zip']) {
                    if ($a['distance'] == $b['distance']) {
                            return 0;
                    }
                    return ($a['distance'] < $b['distance']) ? -1 : 1;
            }
            return ($a['zip'] < $b['zip']) ? -1 : 1;
    }

function processRes($post) {
                 $r2=0;
                 for($i=0; $i < count($post); $i++) {
                       $fetch = $this->zipProx($post[$i]['zipcode'], $post[$i]['radius']);
                        for($f = 0; $f < count($fetch); $f++) {
                                $zips[$r2]['zip'] = "'".$fetch[$f]['zip']."'";
				$zips[$r2]['distance'] = "'".$fetch[$f]['distance']."'";
                                $zips[$r2]['tpid'] = $post[$i]['tpid'];
                                $r2++;
                        }
                 }

             usort($zips, 'cmp');
                    for ($z=1, $j=0, $n=count($zips); $z<$n; ++$z) {
                        if ($zips[$z]['zip'] == $zips[$j]['zip']) {
                           unset($zips[$z]);
                        } else {
                          $j = $z;
                        }
                    }
}

Note: I did strip out most of the other code and just pasted what's relevant here....

[NogDog]

I think you want to do something like:

usort($zips, array($this, 'cmp'));

(See callback type.)

[halojoy]

About comparing 2 numbers.

There are a functions for to compare 2 strings:
[man]strcmp[/man] and [man]strcasecmp[/man] (caseinsensitive)

Same way there is a php function for to compare 2 numbers
[man]bccomp[/man]

int bccomp ( string $left_operand , string $right_operand [, int $scale ] )

Returns 0 if the two operands are equal,
1 if the left_operand is larger than the right_operand,
-1 otherwise.

It wont make any signifcant difference to your function or performance
but can be good to know about this bccomp() function.
When using bccomp() your method becomes:

function cmp($a, $b) {

$z = bccomp($a['zip'], $b['zip']);
if ($z == 0) {
	return bccomp($a['distance'], $b['distance']);
}
return $z;
}