Which is the most effective way to group array elements respect to the values of another array in PHP?
Example:
names = [antonio, luigi, marco, stefano, gennaro, pino, lorenzo];
surnames = [bianchi, rossi, rossi, brambilla, rossi, rossi, brambilla];
expected result:
bianchi:
antonio
rossi:
luigi, marco, gennaro, pino
brambilla:
stefano, lorenzo
Try this
foreach ($surnames as $key => $value) {
if (isset($result[$value])) {
if (!is_array($result[$value])) $result[$value] = (array) $result[$value];
array_push($result[$value], $names[$key]);
}
else
$result[$value]= $names[$key];
}
print_r($result);
Output
Array (
[bianchi] => antonio
[rossi] => Array ( [0] => luigi, [1] => marco, [2] => gennaro, [3] => pino )
[brambilla] => Array ( [0] => stefano, [1] => lorenzo )
)
Otherwise
foreach ($surnames as $key => $value) { $result[$value][] = $names[$key]; }
Output
Array (
[bianchi] => Array ( [0] => antonio )
[rossi] => Array ( [0] => luigi, [1] => marco, [2] => gennaro, [3] => pino )
[brambilla] => Array ( [0] => stefano, [1] => lorenzo )
)
It sounds like you essentially want to create a map where each output element of the map is a list. Try something like this:
<?php
function groupArrays($arrayToGroup, $arrayToGroupBy)
{
if (count($arrayToGroup) != count($arrayToGroupBy))
return null;
$output = array();
for ($i = 0; $i < count($arrayToGroupBy); $i++)
{
$key = $arrayToGroupBy[$i];
$val = $arrayToGroup[$i];
if (!isset($output[$key]))
$output[$key] = array();
array_push($output[$key], $val);
}
return $output;
}
?>
I just quickly create the script, this is the fastest and reliable way:
<?php
$names = ['antonio', 'luigi', 'marco', 'stefano', 'gennaro', 'pino', 'lorenzo'];
$surnames = ['bianchi', 'rossi', 'rossi', 'brambilla', 'brambilla', 'brambilla', 'brambilla'];
$final = [];
foreach ($surnames as $index => $_sur) {
// We don't check isset $names[$index] here
$final[$_sur][] = $names[$index];
}
var_export($final);
