How to check if arrays values match while preserving its order in PHP-CodePudding

What I'm trying to do is preserve the order of an array, while determining if each of the numbers match numbers that were pulled from the database. What I have is an array of numbers ($ids), and a non empty array of rows ($rows)

$images = array();
$ids = array(
    0    => '41',
    1  => '42',
    2  => '43',
    3 => '44'
);
// database example
$rows = array(
    0 => array(
        'name' => 'John Doe',
        'id' => '42'
    ),
    1 => array(
        'name' => 'Jane Doe',
        'id' => '43'
    ),
);
$i = 0;
foreach ($rows as $row) {
   // This works, but it doesn't preserve the order of the $ids array
   if (in_array($row['id'], $ids[$i])) {
      // add $id to a new array
      // or use the same $id array
      $images[$i]['name'] = $row['name'];
      $images[$i]['id'] = $row['id'];
      $i  ;
   }
}

Any help would be appreciated.

CodePudding user response：

Since id is unique in the rows from your database, you can index the $rows array by id to make it easier to look up values there. You can do this with array_column like this:

$rows = array_column($rows, null, 'id');

Or add them to $rows using id as index as you fetch them from the db like this:

while ($row = //whatever query result/prepared statement fetch you're using) {
    $rows[$row['id']] = $row;
}

Then, instead of iterating $rows, you can iterate $ids. This will ensure that the resulting $images array will be in the same order as $ids.

foreach ($ids as $id) {
   if (isset($rows[$id])) {
      $images[] = [
          'name' => $rows[$id]['name'],
          'id' => $rows[$id]['id']
      ];
   }
}

Another thing that might make this easier (unless you're using the non-matching rows for something else), would be to use the $ids array as a parameter to a WHERE id IN clause in the query that's selecting $rows, so you won't have to do that filtering in PHP. Here's a Q&A that shows how to do that with PDO, for example: PHP - Using PDO with IN clause array.

CodePudding user response：

You could iterate over ids array instead. It will be something like this:

foreach($ids as $id) {
    $data = find($id, $rows);
    
    if ($data === null) {
        continue;
    }
    
    $images[] = [
        'name' => $data['name'],
        'id' => $data['id']
    ];
}

function find($id, $rows) {
    foreach($rows as $row) {
        if($row['id'] == $id) {
            return $row;
        }
    }
    
    return null;
}

Totally agree with @Don't Panic, you should fetch only the data you'll use if possible.