function group_by($column_name, $rows) {
$result = [];
$groups = distinct($rows, $column_name);
foreach($groups as $group) {
$result[$group] = where($rows, [$column_name=>$group]);
}
return $result;
}
function distinct($rows, $column_name) {
$column_values = [];
foreach($rows as $row) {
$column_values[$row[$column_name]] = 1;
}
return array_keys($column_values);
}
function where($rows, $params) {
$result = [];
foreach($rows as $row) {
$row_matched = true;
foreach($params as $column_name => $column_value) {
if( !array_key_exists($column_name, $row)
|| $row[$column_name] != $column_value ) {
$row_matched = false;
break;
}
}
if( $row_matched ) $result[] = $row;
}
return $result;
}
$rows = [
['id'=>1, 'name'=>'한놈', 'department_id'=>1, 'birth_date'=>'1999-01-01'],
['id'=>2, 'name'=>'두시기', 'department_id'=>2, 'birth_date'=>'2000-01-01'],
['id'=>3, 'name'=>'석삼', 'department_id'=>2, 'birth_date'=>'1999-01-01'],
['id'=>4, 'name'=>'너구리', 'department_id'=>3, 'birth_date'=>'2000-01-01'],
];
print_r( group_by('birth_date', $rows) );
$rows = [
['id'=>1, 'level'=>'WARN', 'message'=>'name missing'],
['id'=>2, 'level'=>'INFO', 'message'=>'hello'],
['id'=>3, 'level'=>'WARN', 'message'=>'duplicated id'],
['id'=>4, 'level'=>'INFO', 'message'=>'world'],
];
print_r( group_by('level', $rows) );
