manipulating dat retrieved from the DB using php arrays

am querying the DB as follows:

$`result=mysql_query("SELECT name,itemquantity FROM mytable WHERE price='$price'");`

now,i want to create an array to insert the values that are as a result of this query e'g let's say this is the resultant data:

name itemquantity price john 10 100 joel 20 100 brian 10 100

how do I create an array to insert the above data using $name and $quantity as variables;
secondly,(this is a trading platform),so let's say a user wanted to buy 25 items from the data in the array,and so to achieve this the script has to take the 10 items from john and 15 from joel(that adds up to 25) and then set their items to the remaining value i.e john's items=0 and joel's items=5.how do I code this.please assist. i've tried to simplify this the best i can .thanks