PHP has a fantastically useful range of
functions for handling Arrays. I found that there were a couple of situations that I was habitually facing which they didn't handle. These related to 2D arrays returned by SQL that I needed to rearrange in different ways.
The first function is
Array_Arrange_By() and is shown below:
function Array_Arrange_By($arr, $key, $key2 = null) {
$out = array();
if (!$arr) {
return $out;
}
foreach ($arr as $k => $row) {
if (is_array($key2)) {
@$out[$row[$key]][] = $row;
} else if ($key2) {
$out[$row[$key]] = $row[$key2];
} else {
$out[$row[$key]] = $row;
}
}
return $out;
}
This function will reindex this array in one of 3 ways:
array([0] => array('id' => 1,'b' => 'dog','cst' => 20),
[1] => array('id' => 4,'b' => 'cat','cst' => 60),
[2] => array('id' => 8,'b' => 'cat','cst' => 80),
[3] => array('id' => 9,'b' => 'cat','cst' => 90));
var_export (Array_Arrange_By($a, 'id'));
Gives:
array (
1 =>
array (
'id' => 1,
'type' => 'dog',
'cst' => 20,
),
4 =>
array (
'id' => 4,
'type' => 'cat',
'cst' => 60,
),
8 =>
array (
'id' => 8,
'type' => 'cat',
'cst' => 80,
),
9 =>
array (
'id' => 9,
'type' => 'cat',
'cst' => 90,
),
)
It's very useful as the array returned contains the same information but is indexed by the 'id' field.
Alternatively you might only want one of the non-id fields from the original array.
array([0] => array('id' => 1,'type' => 'dog','cst' => 20),
[1] => array('id' => 4,'type' => 'cat','cst' => 60),
[2] => array('id' => 8,'type' => 'cat','cst' => 80),
[3] => array('id' => 9,'type' => 'cat','cst' => 90));
print_r (Array_Arrange_By($a, 'id', 'type'));
Giving:
array (
1 => 'dog',
4 => 'cat',
8 => 'cat',
9 => 'cat',
)
This might be a very useful lookup array.
Finally sometimes you may want to perform the equivalent of a PHP level
group by operation.
array([0] => array('id' => 1,'type' => 'dog','cst' => 20),
[1] => array('id' => 4,'type' => 'cat','cst' => 60),
[2] => array('id' => 8,'type' => 'cat','cst' => 80),
[3] => array('id' => 9,'type' => 'cat','cst' => 90));
print_r (Array_Arrange_By($a, 'type', array()));
Gives:
array (
'dog' =>
array (
0 =>
array (
'id' => 1,
'type' => 'dog',
'cst' => 20,
),
),
'cat' =>
array (
0 =>
array (
'id' => 4,
'type' => 'cat',
'cst' => 60,
),
1 =>
array (
'id' => 8,
'type' => 'cat',
'cst' => 80,
),
2 =>
array (
'id' => 9,
'type' => 'cat',
'cst' => 90,
),
),
)
This array gives a really nice way to now generate a 2 Level table. In this case iterating through the different types and then each of the records with that type.
