public function column($column_key, $index_key = null)
{
if (function_exists('array_column')) {
return array_column($this->items, $column_key, $index_key);
}
$result = [];
foreach ($this->items as $row) {
$key = $value = null;
$keySet = $valueSet = false;
if (null !== $index_key && array_key_exists($index_key, $row)) {
$keySet = true;
$key = (string) $row[$index_key];
}
if (null === $column_key) {
$valueSet = true;
$value = $row;
} elseif (is_array($row) && array_key_exists($column_key, $row)) {
$valueSet = true;
$value = $row[$column_key];
}
if ($valueSet) {
if ($keySet) {
$result[$key] = $value;
} else {
$result[] = $value;
}
}
}
return $result;
}