Creating an array of associative arrays in PHP

Question

I am fetching rows from the DB and returning the result in JSON. The output needs to be an array of associative arrays.

$i = 0; foreach($resultSet as $r) { $output[$i]['key1'] = $r['col1']; $output[$i]['key2'] = $r['col2']; ... $output[$i]['keyN'] = $r['colN']; $i++; } 

Is there a more elegant way to do this? Is there anything wrong with this approach? If yes, what is it?

Answer 1

Instead of declaring $i=0; before the loop, you can also write :

foreach($resultSet as $i => $r) { $output[$i]['key1'] = $r['col1']; $output[$i]['key2'] = $r['col2']; ... $output[$i]['keyN'] = $r['colN']; } 

Also, if you could rename your column in the DB query, you could have :

foreach($resultSet as $i => $r) { $output[$i] = $r; } 

Which is pretty much like doing $output = $resultSet;

Edit : If you do need to do some processing on $resultSet for whatever reason and you'd rather have different names, you can consider doing :

for (array('key1' => 'col1', ... 'keyN' => 'colN' as key => col) { $output[$i][$key] = $r[$col]; } 

Answer 2

Assuming you are trying to map Columns from the resulting rows such that:

Row | Column 1 | Column 2 1 | Value 1 | Value 2 2 | Value 2 | Value 2 

Results in:

$rows = array( 1 => array( 'Column 1' => 'Value 1', 'Column 2' => 'Value 2' ), 2 => array( 'Column 1' => 'Value 1', 'Column 2' => 'Value 2' ), ); 

If your PDO returns the values in numerical position, you can do this:

$columns = array( 'Column 1', 'Column 2' ); $rows = array_map(function($row) use ($columns) { return array_combine($columns, $row); }, $resultSet); 

Or, if the $resultSet is associative, and you want to keep the names:

$columns = array_flip(array( 'Column 1', 'Column 2' )); $rows = array_map(function($row) use ($columns) { return array_intersect_key($row, $columns); }, $resultSet); 

OR, if your PDO returns them in an Associative array, but the Column names need to be change:

$columns = array( 'Column 1' => 'Key 1', 'Column 2' => 'Key 1' ); $rows = array_map(function($row) use ($columns) { $return = array(); foreach($columns as $from => $to) { $return[$to] = !empty($row[$from]) ? $row[$from] : NULL; } return $return; }, $resultSet); 

That last one would work for either situation, really, as it will take the value at $row[$from] and place it at $result[$to], which would account for numerical indices or string indices. Also, the empty() check will suppress PHP errors, and will ensure that you have a value at each position.

Answer 3

Perhaps something like this?

$i = 0; foreach($resultSet as $key => $value){ $output[$i++][$key] = $value; } 

Given a $resultSet like this:

$resultSet['key0'] = 'value0'; $resultSet['key1'] = 'value1'; $resultSet['key2'] = 'value2'; $resultSet['key3'] = 'value3'; $resultSet['key4'] = 'value4'; $resultSet['key5'] = 'value5'; 

The above code will produce something as follows:

Array ( [0] => Array ( [key0] => value0 ) [1] => Array ( [key1] => value1 ) [2] => Array ( [key2] => value2 ) [3] => Array ( [key3] => value3 ) [4] => Array ( [key4] => value4 ) [5] => Array ( [key5] => value5 ) ) 

Echoing $output[0]['key0] will output value0 (or an array if value0 is an array).

As a side note, you could actually get completely rid of $i, and just do the following:

foreach($resultSet as $key => $value){ $output[][$key] = $value; } 

Do let me know if I completely misunderstood the question at hand though :)