Question

I’ve got three strings generated from a long process of combined queries and file reads, each related to the other.

---

Example:

$versions = "1 2 5 4 10 6 8 7 3 9";
$weights = "50.2 60.5 35 10 15.98 60 50 60.1 70 75";
$ids = "512 318 112 326 155 191 977 961 943 441";

I would like to sort them in ascending order according to version number.

Example result:

$versions = "1 2 3 4 5 6 7 8 9 10";
$weights = "50.2 60.5 70 10 35 60 60.1 50 75 15.98";
$ids = "512 318 943 326 112 191 961 977 441 155";

---

My question is: is there a more efficient way of doing this than I am currently doing it?
Note that these strings can become big, largest I’ve seen so far is ~600 different versions

I do the following:

• explode strings
• copy arrays with version number as keys
• sort arrays by keys
• implode strings back

Here’s the code and a live example:

$versions = "1 2 5 4 10 6 8 7 3 9";
$weights = "50.2 60.5 35 10 15.98 60 50 60.1 70 75";
$ids = "512 318 112 326 155 191 977 961 943 441";

$a_versions = explode(" ", $versions);
$a_weights = explode(" ", $weights);
$a_ids = explode(" ", $ids);

$s_versions = array();
$s_weights = array();
$s_ids = array();

//set keys to correspond to version number
foreach($a_versions as $key => $ver){
    $s_versions[$ver] = $a_versions[$key];
    $s_weights[$ver] = $a_weights[$key];
    $s_ids[$ver] = $a_ids[$key];
}

//sort according to keys
ksort($s_versions, SORT_NUMERIC);
ksort($s_weights, SORT_NUMERIC);
ksort($s_ids, SORT_NUMERIC);

//implode back
$versions = implode(" ", $s_versions); 
$weights = implode(" ", $s_weights); 
$ids = implode(" ", $s_ids); 

echo "
    <pre>
        $versions
        $weights
        $ids
    </pre>
";

/*==========
Results
    1 2 3 4 5 6 7 8 9 10
    50.2 60.5 70 10 35 60 60.1 50 75 15.98
    512 318 943 326 112 191 961 977 441 155
==========*/

---

Performance increase #1:

Replacing the foreach loop with array_combine might give a little performance gain. – svens

Indeed it did, according to a simple unit test, it’s about 11-15% faster.

Answer 1

This is the best I could find:

$versions = array_flip(explode(' ', $versions));
$weights = explode(' ', $weights);
$ids = explode(' ', $ids);

ksort($versions, SORT_NUMERIC);
foreach ($versions as $version => $idx) {
  $result[0][] = $version;
  $result[1][] = $weights[$idx];
  $result[2][] = $ids[$idx];
}

return array(
  implode(' ', $result[0]),
  implode(' ', $result[1]),
  implode(' ', $result[2]),
);

See:
http://codepad.viper-7.com/flcvnO
for a comparison of what I tested (including you initial code and the one with array_combine)