如何在PHP关联数组中按$ value对SQL查询结果进行排序？

Question

I have an array which is the result of an SQL query. When I print_r($results) I get

Array ( [0] => Array ( [Q1] => 24 ) ) Array ( [0] => Array ( [Q2] => 12 ) ) Array ( [0] => Array ( [Q3] => 14 ) ) Array ( [0] => Array ( [Q4] => 10 ) ) etc.

When I display contents in HTML with a foreach ($result as $key=>$value) loop, I get

-----------
|Q1 |   24|
|Q2 |   12|
|Q3 |   14|
|Q4 |   10|
-----------

But I'd like to sort the array by value so that I get

-----------
|Q4 |   10|
|Q2 |   12|
|Q3 |   14|
|Q1 |   24|
-----------

The second column is the product of a calculation, and not an actual DB column, so I can't use ORDER BY in the SQL. Here's the query itself:

SELECT (SUM(Q".$i.")) AS Q$i FROM marks

I've tried sort functions - arsort($results) and others. I've tried reassigning to 2D arrays - $final_result[] = $results; and sorting - but no luck.

Is there some trick I'm missing in my attempt to access the actual values in $results? (24, 12, 14 etc)

Answer 1

With a combination of usort (user-function sort), strcmp (string comparison) and key (for the variable keys) you can handle this:

$quarters = array(
    array(
        'Q1' => 24
    ),
    array(
        'Q2' => 12
    ),
    array(
        'Q3' => 14
    ),
    array(
        'Q4' => 10
    )
);

usort($quarters, function($a, $b) {
    return reset($a) - reset($b);
});

print_r($quarters);

Gives us:

Array
(
    [0] => Array
        (
            [Q4] => 10
        )

    [1] => Array
        (
            [Q2] => 12
        )

    [2] => Array
        (
            [Q3] => 14
        )

    [3] => Array
        (
            [Q1] => 24
        )

)

Answer 2

I found a way to sort the results of my query. It's a workaround.

The problem was that my query SELECT FLOOR(SUM(Q".$i.")) AS Q$i FROM table didn't yield an associative array that asort(), usort() etc could handle.

When I did a var_export($results) it output:

array ( 0 => array ( 'Q1' => '24', ), )array ( 0 => array ( 'Q2' => '12', ), )array ( 0 => array ( 'Q3' => '14', ), )array ( 0 => array ( 'Q4' => '10', ), )

Note the non-incrementing 0; this seems to be why the sort algorithms aren't working.

However, I was able to display the query results in a foreach loop without a problem to give:

-----------
|Q1 |   24|
|Q2 |   12|
|Q3 |   14|
|Q4 |   10|
-----------

So my solution was to reassign the query results to an associative array in that loop, as follows:

foreach ($results as $result) 
      { 
            foreach ($result as $key=>$value)
                { 
            $rankings["$key"]="$value"; 
            } 
          }
   }

Now, a var_export($rankings) reveals the data structure I would expect:

array ( 'Q1' => '24', 'Q2' => '12', 'Q3' => '14', 'Q4' => '10', )

And this new array was amenable to sorting:

asort($rankings);

-----------
|Q4 |   10|
|Q2 |   12|
|Q3 |   14|
|Q1 |   24|
-----------