Merge same items and add their quantity

Question

I need help. How to code this in PHP? If I am using a form method to input item# and quantity

form method="post"<br />
input type="number" name="item1" | input type="number" name="quantity1"<br />
input type="number" name="item2" | input type="number" name="quantity2"<br />
input type="number" name="item3" | input type="number" name="quantity3"<br />

So, if I put same item# then the quantity will add their values. Thanks in advance.

Input: ( form method ) 

Item#: Quantity: 

111       2 

222       5 

111       6 


Output: 

Item#: Quantity: 

111      8 

222      5 

Answer 1

function group_items($string=""){
    if(!$string){return;}
    $grouped=array();
    preg_match_all('/([0-9\.]+(?: [0-9\.]+)?)/',$string,$matches);
    $string='';
    $matches = isset($matches[0])?$matches[0]:array();
    foreach($matches as $match){
        $exp = explode(' ',$match);
        if(!isset($grouped[$exp[0]])){
            $grouped[$exp[0]] = $exp[1];
        }else{
            $grouped[$exp[0]] += $exp[1];
        }
    }
    foreach($grouped as $key => $group){
        $string.=$key." ".$group." ";
    }
    return trim($string);
}   

calling it by:

echo group_items("111 2 222 5 111 6");

output:

 111 8 222 5