[SOLVED] Group 2d array data by the values in a column

Group 2d array data by the values in a column

I'm struggling with results from a database fetch.

Let's say I have some rows:

array('id'=>1, 'surname'=>'rossi', 'name'=>'mario', 'group'=>'admin'), 
array('id'=>2, 'surname'=>'rossi', 'name'=>'giovanni', 'group'=>'user'), 
array('id'=>3, 'surname'=>'verdi', 'name'=>'luigi', 'group'=>'user'), 
array('id'=>4, 'surname'=>'verdi', 'name'=>'franco', 'group'=>'guest'), 
array('id'=>5, 'surname'=>'bianchi', 'name'=>'mario', 'group'=>'guest')

now what do I have to do to put these 5 rows into a grouped array?

example:

user = array(
   array('id'=>2, 'surname'=>'rossi', 'name'=>'giovanni', 'group'=>'user'), 
   array('id'=>3, 'surname'=>'verdi', 'name'=>'luigi', 'group'=>'user'))
guest = array(
   array('id'=>4, 'surname'=>'verdi', 'name'=>'franco', 'group'=>'guest'), 
   array('id'=>5, 'surname'=>'bianchi', 'name'=>'mario', 'group'=>'guest')) 
admin = array(
   array('id'=>1, 'surname'=>'rossi', 'name'=>'mario', 'group'=>'admin'))

Solution

// get query result
$result = mysql_query(...);

// prepare the target array
// it will hold user groups having group name as key
// eg. "user" => Array(), "guest" => Array()
$users = Array();

// whlile fetching rows from the result, add each row into $row["group"] key of target
while($row = mysql_fetch_assoc($result))
   $users[$row["group"]][] = $row;

// free the mysql result
mysql_free_result($result);

Update: There is no real need to define the keys in the target $user variable. to make code readable and manageable it is enough to comment on the general structure.