PHP - Php Adding And Subtracting

Good morning. I need to subtract stock levels from oldest stock first then to the next date.

It is allowed to move into negative values.

example

01-10  stock in 10  stock out 5 - stock count 5

02-10 stock in 10 stock out 7 stock count ... here we need to subtract the 7 from previous days 5 til it reches 0  then stock in subtraction

 01-10 stock =0

02-10 stock = 8 --- as 7 -5 gives me -2 in incoming stock is 10 leaving me with stock count of 8.

03-10 stock in 8 stock out 21 

02-10 stck level must be    0

03-10 stock lever now is 8-14 = -6 and so on

below is my code. 

    $lq_in = new ListQuery('stock_audit5f5795042f369');
    $lq_in->addSimpleFilter('name', '%PEPPER yellow%', 'LIKE' );
    //$lq_in->addSimpleFilter('product_id', $product_id, '=');
    $lq_in->setOrderBy('date_entered');
    $res_in = $lq_in->fetchAll();
$StockArray = [];
foreach($res_in as $out_rec) {
    /*$upd_out = array();
    $upd_out['stock_out_done'] = 0;

    $out_rec_u = ListQuery::quick_fetch('stock_audit5f5795042f369', $out_rec->getField('id'));
    $aud_upd_out = RowUpdate::for_result($out_rec_u);
    $aud_upd_out->set($upd_out);
    $aud_upd_out->save();
    continue;
    */
    $stock_out = $out_rec->getField('stock_out');
    $stock_out_done = $out_rec->getField('stock_out_done');
    $date_entered = $out_rec->getField('date_entered');
    $product_id = $out_rec->getField('product_id');

    
    //echo '<pre>';
   // print_r($out_rec->row);
    $StockItems[] = $out_rec->row;

    //$stock_done = 0;
    /*
    foreach($res_in as $in_rec) {
        $upd = array();
        if($stock_out_new > $in_rec->getField('stock_level')) {
            $upd['stock_level'] = 0;
            $stock_out_new = $stock_out_new-$in_rec->getField('stock_level');
            $stock_done = $in_rec->getField('stock_level');
        } elseif ($stock_out_new == $in_rec->getField('stock_level')) {
            $upd['stock_level'] = 0;
            $stock_out_new = 0;
            $stock_done = $stock_out;
        } elseif($stock_out_new < $in_rec->getField('stock_level')) {
            $upd['stock_level'] = $in_rec->getField('stock_level')-$stock_out_new;
            $stock_out_new = 0;
            $stock_done = $stock_out;
        } else {
            continue;
        }

        $in_rec_u = ListQuery::quick_fetch('stock_audit5f5795042f369', $in_rec->getField('id'));
        $aud_upd = RowUpdate::for_result($in_rec_u);
        $aud_upd->set($upd);
        $aud_upd->save();

        if($stock_out_new == $stock_done)
            break;
    }
    
    $upd_out = array();
    $upd_out['stock_out_done'] = $stock_done;

    $out_rec_u = ListQuery::quick_fetch('stock_audit5f5795042f369', $out_rec->getField('id'));
    $aud_upd_out = RowUpdate::for_result($out_rec_u);
    $aud_upd_out->set($upd_out);
    $aud_upd_out->save();
    */
}
function GetFirstItemWithStockKey($StockItemsarrayk = null){
    if($StockItemsarrayk != null){
        foreach($StockItemsarrayk as $key => $value){
            if(((int) $StockItemsarrayk[$key]['stock_level']) > 0){
                return $key;
            }
        }
    }
}

function SetFirstItemWithStock($StockItemsarray = null){
    if($StockItemsarray != null){
        foreach($StockItemsarray as $key => $value){
            if(((int) $StockItemsarray[$key]['stock_level']) > 0){
                return $StockItemsarray[$key];
            }
        }
    }
}
$remainder = 0;
$pkey = "";
$StockLevelKey = 0;
$StockIn = [];
$StockOut = [];
$InStock = [];

$NewStockItems = $StockItems;
$ArrayKeys = [];
foreach($StockItems as $key => $value){
  $StockIn[$key] = (int) $StockItems[$key]['stock_in'];
  $StockOut[$key] = (int) $StockItems[$key]['stock_out'];
  $InStock[$key] = (int) $StockItems[$key]['stock_level'];
  $ArrayKeys[] = (int)$key;
  
}
//var_dump($InStock);
foreach($NewStockItems as $key => $value){
    if($key < 1){
        if($StockIn[$key] > 0 && $StockOut[$key] == 0 && $InStock[$key] == 0){
            $StockItems[$key]['stock_level'] = ($InStock[$key] + $StockIn[$key]);     
        }
        if($StockIn[$key] == 0 && $StockOut[$key] > 0 && $InStock[$key] == 0){
            $StockItems[$key]['stock_level'] = ($InStock[$key] - $StockOut[$key]);
         
        }
        if($StockIn[$key] > 0 && $StockOut[$key] > 0 && $InStock[$key] == 0){
            $StockItems[$key]['stock_level'] = ($InStock[$key] - $StockOut[$key] + $StockIn[$key]);
            $StockItems[$key]['stock_out'] = 0;
        }
    }
    if($key > 0){
        $previousWithStockItem = SetFirstItemWithStock($StockItems);
        $previousItemWithStockKey = GetFirstItemWithStockKey($StockItems);
       // echo "<pre>";
      //  print_r($previousWithStockItem);
       // var_dump($StockIn[$key]); echo "&nbsp;&nbsp;&nbsp;&nbsp;--IN";
      //  var_dump($InStock[$key]); echo "&nbsp;&nbsp;&nbsp;&nbsp;--- current";
       // var_dump($StockOut[$key]); echo "&nbsp;&nbsp;&nbsp;&nbsp;--- OUT";
        while($StockOut[$key] > 0){
            if($StockOut[$key] > 0 && $previousWithStockItem['stock_level'] > 0){
                $Counter = 0;
                $maxIteration = 0;
                for($Counter = $previousWithStockItem['stock_level']; $Counter >= 0; $Counter--){
                    $StockItems[$previousItemWithStockKey]['stock_level'] = $Counter;
                    if($Counter == 0){
                         $StockOut[$key] = $StockOut[$key] - $maxIteration;
                    }
                    $maxIteration++;
                }
            }
            if((((int) $StockItems[$key]['stock_level'] < 0) || ((int) $StockItems[$key]['stock_level'] === 0))&& ($StockIn[$key] > 0)){
                $valueTotal = $StockItems[$key]['stock_level'] + $StockIn[$key];
                $StockItems[$key]['stock_level'] = $valueTotal;
            }
            echo "<hr/>";
            echo (int) $StockOut[$key];
            echo "<br/>";
             echo (int) $StockItems[$key]['stock_level'];
            echo "<br/>";
             echo "<hr/>";
            if(((int) $StockOut[$key] > 0) && ((int) $StockItems[$key]['stock_level'] > 0) && ((int) $StockItems[$key]['stock_level'] > $StockOut[$key])){
              
                $newStockLevel = $StockItems[$key]['stock_level'] - $StockOut[$key];
                echo $newStockLevel;
                $StockItems[$key]['stock_level'] = $newStockLevel;
                $StockItems[$key]['stock_out'] = 0;
                $StockOut[$key] = 0;
            }
            if((((int) $StockItems[$key]['stock_level'] < 0) || ((int) $StockItems[$key]['stock_level'] === 0))&& ($StockIn[$key] > 0)){
                $valueTotal = $StockItems[$key]['stock_level'] + $StockIn[$key];
                echo $valueTotal;
                $StockItems[$key]['stock_level'] = $valueTotal;
            }
        }
    }
}
echo "<table><tr><td><pre>";
print_r($NewStockItems);
echo "</pre></td><td><pre>";
print_r($StockItems);
echo "</pre></td></table>";
/*
        if($StockIn[$key] > 0 && $StockOut[$key] >0 && $InStock[$key] == 0){
            $StockItems[$key]['stock_level'] = ($InStock[$key] + ($StockIn[$key] + $StockOut[$key]));
            
            $StockOut[$key] = 0;
            $StockItems[$key]['stock_out'] = 0;
        }
        if($StockIn[$key] != 0 && $StockOut[$key] != 0 && $InStock[$key] != 0){
            $StockItems[$key]['stock_level'] = ($InStock[$key] - ($StockOut[$key] + $StockIn[$key]));
            
            $StockOut[$key] = 0;
            $StockItems[$key]['stock_out'] = 0;
        }*/
/**
 @Rule 1 
 # Stockin has value and stock_out = 0 and stock_level = 0 and stock_out_done = null, actualstock to show actual stock level;
 # 
 
 */

/*if($StockCalculation[$Skey]['stock_out'] >= $StockItems[$key]['stock_level']){
                           $StockItems[$key]['stock_out'] = ($StockItems[$key] - 1);
                           $StockItems[$key]['stock_level'] = ($StockItems[$key]['stock_level'] - 1);
                           // If StockOut == 0 next StockOutItem
                           if($StockCalculation[$Skey]['stock_out'] == 0){
                               $remainder = 0;
                                continue;
                           }elseif($StockItems[$key]['stock_level'] == 0){
                               //CurrentInStock == 0 then continue to next CurrentItem
                                $remainder = $StockItems[$key]['stock_out'];
                                continue(2);
                           }
                       }
 $CurrentStockIn = $StockItems[$key]['stock_in'];
   $CurrentStockOut = $StockItems[$key]['stock_out'];
   $CurrentInStock = $StockItems[$key]['stock_level'];
   if($key == 0){
       if($CurrentStockIn > 0 && $CurrentStockOut === 0 && $CurrentInStock == 0){
           $CurrentInStock = $CurrentStockIn;
           //Query update stock level set = stock_in 
           //"UPDATE STOCK SET stock_level = {$CurrentStockIn} where id = {$StockItems[$key]['id']}";
           $StockItems[$key]['stock_level'] = $CurrentStockIn;
       }
       if($CurrentStockIn != 0 && $CurrentStockOut != 0 && $CurrentInStock == 0){
           //Query Update Stocklevel if stock_out > 0 and stock_level = 0
           //"UPDATE STOCK SET stock_level = "+($CurrentStockIn - $CurrentStockOut) + "where id = {$StockItems[$key]['id']}";
           if($CurrentStockIn > $CurrentStockOut && $CurrentStockOut == 0){
               $StockItems[$key]['stock_out'] = 0;
               $StockItems[$key]['stock_level'] = $CurrentInStock = $CurrentStockIn - $CurrentStockOut;
           }
           if($CurrentStockOut > $CurrentStockIn){
               $StockItems[$key]['stock_level'] = $CurrentInStock = $CurrentInStock - $CurrentStockOut;
           }
       }
       if($CurrentInStock != 0 && $CurrentStockOut > 0){
            //If Current in stock below 0 and stock out > 0 then negative more
           //"UPDATE STOCK SET stock_level = "+($CurrentInStock - $CurrentStockOut) + "where id = {$StockItems[$key]['id']}";
           $StockItems[$key]['stock_level'] = $CurrentInStock = ($CurrentInStock - $CurrentStockOut);
           $StockItems[$key]['stock_out'] = 0;
       }
        if($CurrentInStock != 0 && $CurrentStockIn > 0){
            
            //If Current in stock below 0 and stock out > 0 then negative more
           //"UPDATE STOCK SET stock_level = "+($CurrentInStock - $CurrentStockOut) + "where id = {$StockItems[$key]['id']}";
           $StockItems[$key]['stock_level'] = $CurrentInStock = ($CurrentInStock + $CurrentStockIn);
       }
       // Run row update for first item
   }else{
       foreach($StockCalculation as $Skey => $Sval){
           $NextStockOut = $Sval['stock_out'];
           $NextStockIn = $Sval['stock_in'];
           $NextStockLevel = $Sval['stock_level'];
           
           if($Skey > 0 && $key > 0){
              // print_r($NextStockOut);
                   for($i = $NextStockOut; $i >= -1; $i--){
                       if($NextStockOut > 0){
                           if($NextStockOut > 0){
                               /* if($StockItems[$StockLevelKey]['stock_level'] != 0){
                                    $StockItems[($StockLevelKey)]['stock_level'] = ($StockItems[($StockLevelKey)]['stock_level'] - 1);
                                    //$StockItems[($Skey-1)]['stock_out'] = ($StockItems[($Skey-1)]['stock_out'] -1);
                                }
                                if($StockItems[($Skey-1)]['stock_level'] != 0){
                                    $StockItems[($Skey-1)]['stock_level'] = ($StockItems[($Skey-1)]['stock_level'] - 1);
                                }
                           }
                       }
                       $NextStockOut = ($NextStockOut -1);
                       if($NextStockOut != 0){
                           $StockItems[$Skey]['stock_out'] = 0;
                           
                           break;
                       }
                       
                   }
               
           }
           unset($StockCalculation[$Skey]);
       }
   }/*
*/

This might be more of a mySQL question or a PHP question, I'm not exactly sure.  I have a field in my table (Deals) called "Price".  All I want is the sum of that field.

I tried using something like:

$price += $row['Price'];

This ended up as one long string, even though the database is set as a decimal number field.

Then I tried doing it from mySQL like this (from what I read), but I don't think I have the full answer:

foreach($stmt->query('SELECT SUM(Price) 
        FROM Deals') as $row) {
            echo "<tr>";
            echo "<td>Total</td>";
            echo "<td> ->".$row['SUM(Price)']."</td>";
            echo "</tr>";
        }

Anyway, if someone could just show me how to get that sum, I would greatly appreciate it because I am missing something here.