PHP如果变量只有重复只显示第一个实例？

I've created a mysql table that includes these rows & values:

   category | item_name
   ======================= 
   Dinner   |  Lobster
   Dinner   |  Pizza
   Lunch    |  Sandwich
   Lunch    |  Soup
   Lunch    |  Salad
  -------------------------

I then query the database, the result is placed in an array "$menu_selected". I loop through "$menu_selected" to display the results.

    foreach($menu_selected as $m):
           echo $category = $m->category . "<br>";
           echo $item_name = $m->item_name . "<br><br>";
    endforeach;

Output:

    Dinner
    Lobster

    Dinner
    Pizza

    Lunch
    Sandwich

    Lunch
    Soup

    Lunch
    Salad

How can I filter the categories in PHP so it doesn't echo each category only the first instance of category? The category row value isn't always going to be "Dinner" or "Lunch", I want to be able to echo the category without comparing it to a constant like if($category =='Dinner'){}. I've spend a week researching and can't figure it out. Anyone's help would be greatly appreciated.

I want the output to look like this:

 **Dinner**
 Lobster
 Pizza
 Sandwich

 **Lunch**
 Sandwich
 Soup
 Salad

Make sure you order by category on your query. Then simply add a $category variable outside your loop, and if that variable has changed, output your header.

$category = '';
foreach($menu_selected as $m) {
     if ($m->category != $category) {
        echo "**$m->category** <br>";
        $category = $m->category;
     }
     echo $m->category . "<br>";
     echo $m->item_name . "<br><br>";
}

Just use 2 foreach method. First one for category second one for items

foreach($menu_selected as $m1):
       echo $category = $m1->category . "<br>";        
    foreach($menu_selected as $m):
       echo $item_name = $m->item_name . "<br><br>";
            if ($m->category != $m1->category) 
                    {
                      break;
                    }
    endforeach;
endforeach;

$cat_item_array = ARRAY();

foreach($menu_selected as $m) {
    if (!isset($cat_item_array[$m->category])) {
     $cat_item_array[$m->category] = $m->item_name;
     echo "found new category: ".$m->category . " (Added item: ".$m->item_name.")<br>";
     continue;
   }
    $cat_item_array[$m->category] = $m->item_name;
    echo "Added item ".$m->item_name." to category ".$m->category.".<br><br>";
}

print '<pre>'; var_dump($cat_item_array); print '</pre>';