Parsing one col of multiple rows php

Question

I have e.g. the following data returned from a query, each name is an item:

id      name      comment
1       FF        hey
1       FF        hey back!
2       L         


        

Answer 1

Don't confuse data access with output and you will have an easier time attacking this sort of problem.

//Fetch and Sort
$data = array();
while ($row = mysql_fetch_array($result)){
   $item = $row['item'];
   if(!isset($data[$item]) {
     $data[$item] = array():
   }
   $data[ = $data[$item][] = $row['comment'];   
}

//Output
foreach($data as $item => $comments) {
    echo '<li><div class=className><div class=itemName>'.$item.'</div>';
    foreach($comments as $comment) {
      echo '<div class=newRow>'.$comment.'</div>'; 
    }
    echo '</div></li>';
}

Answer 2

You can use GROUP_CONCAT() on your mysql query to group all the comments together for each name

SELECT id, name
GROUP_CONCAT(comment) AS comment
FROM table
GROUP BY name;

then explode() the $row[comment] in your php code

while ($row = mysql_fetch_array($result)){

echo '<li><div class=className><div class=itemName>'.$row['name'].'</div>';

    if($row['comment'] != ""){

       $comments = explode(",",$row['comment']);
       foreach($comments as $comment){
               echo '<div class=newRow>'.$comment.'</div>';
       } 

    }

echo '</div></li>';

}

Edit
Thanks to @CBroe, I now know that GROUP_CONCAT() has a group_concat_max_len default of 1024. You will want to increase this before running the GROUP_CONCAT() query -

SET [GLOBAL | SESSION] group_concat_max_len = 10240; // must be in multiples of 1024
SELECT id, name
GROUP_CONCAT(comment) AS comment
FROM table
GROUP BY name;

you will also need to be aware of max_allowed_packet as this is the limit you can set var_group_concat_max_len to.

note: mysql_query() does not allow multiple queries, so you will need to do 2 mysql_query(), and you can use SET SESSION ... so that all queries in your current session have that max_len. It would be better to change from mysql_ functions (which are depreciated) and change to mysqli_ or PDO as they offer multiple query option. also check out - http://php.net/manual/en/mysqlinfo.api.choosing.php

Answer 3

If you are not getting the data back sorted by id already, add to the end of your query:

ORDER BY name

which will retrieve the same list ordered by id. Then in your while loop, add a variable that keeps track of the last item name that you saw. If it changes, add a new li, otherwise, add the comment on to the end of your current list.