php foreach loop undefined property / index notice while setting value to stdclass property or array variable

Question

In foreach loop, I am trying to add some additional property for the source array or objects. That gives me the following notice.

Notice: Undefined property: stdClass::$total

foreach ($this->products as $p_row) {
    $this->data[ $p_row->group_id ][] = $p_row;
    // getting index error here
    $p_row->total += gs_get_product_qty_price($p_row->product, $p_row->qty);
}

However, if I add annotation @ the error is gone.

foreach ($this->products as $p_row) {
    $this->data[ $p_row->group_id ][] = $p_row;
    // adding @ the error gone
    @$p_row->total += gs_get_product_qty_price($p_row->product, $p_row->qty);
}

As far as I understood is on the first iteration, it is not defined; maybe that is why showing an error.

Can anyone explain to me to clear my thought, and is it okay to use @ to avoid error?

The same notice occurs if I try to set data in

Notice: Undefined index: total

$this->data[$p_row->group_id]['total'] += gs_get_product_qty_price($p_row->product, $p_row->qty);

Is it the solution?

foreach ($this->products as $p_row) {

    $p_row->total = 0;

    $this->data[ $p_row->group_id ][] = $p_row;
    $p_row->total                     += gs_get_product_qty_price($p_row->product, $p_row->qty);

}

All you need to do is to define the property before the loop. `$p_row->total = 0;`. You should really avoid using `@` since that can make debugging a massive pain (since it suppresses any potential error message that you do want while debugging. — M. Eriksson, Dec 29 '20 at 06:27
@MagnusEriksson I see, but the `$p_row` is only available in the loop. How can I define it outside the loop? — Code Lover, Dec 29 '20 at 06:30
Ah yes, you're correct. Well, if the properties doesn't exist before the loop, you can simply define it by using `=` instead of `+=` in the loop. If you use `+=`, it's adding to the existing value. But if that property doesn't exist (and that's always the case here), then just define the property instead of adding to it: `$p_row->total = gs_get_procuct_qty_price(....);` — M. Eriksson, Dec 29 '20 at 06:47
@MagnusEriksson the `total` has to be calculated by the `qty` and the `price`. The `qty` is a property in `$p_row` and `price` I have to get it dynamically using the product id. So I can get the total for the array item (a record). Please have a look the modified question. Is that the correct way? — Code Lover, Dec 29 '20 at 07:00

score 0 · Answer 1 · answered Dec 29 '20 at 06:28

0

I think in foreach loop you can't add an index, you have to create index before loop. @ is just ignore Notices. And in last your code, a "=" is extra.

answered Dec 29 '20 at 06:28

Ali Fakoor

82
2

Yes, I understand that but how can I define a property for `$p_row` before the loop? As it is only available within the loop. I have removed extra `=` added by mistake. – Code Lover Dec 29 '20 at 06:31
Ah! so did in this way and that works. `foreach ($this->products as $p_row) { $p_row->total = 0; .. }` Is it the correct way? – Code Lover Dec 29 '20 at 06:36
1

@CodeLover yes, I think it is because that operator "+=" has to have an initial value for work. – Ali Fakoor Dec 29 '20 at 06:57
Got it. Thanks :) Understood the reason. – Code Lover Dec 29 '20 at 07:00

Hammad Ahmed khan · Answer 2 · 2020-12-29T06:44:53.047

0

since $this->data[$p_row->group_id]['total'] it is not defined first and you are $this->data[$p_row->group_id]['total']+= adding value to it it is throwing error. you can use this :

if(isset($this->data[$p_row->group_id]['total'])){
$this->data[$p_row->group_id]['total']+=gs_get_product_qty_price($p_row->product, $p_row->qty);
}else{
$this->data[$p_row->group_id]['total']= gs_get_product_qty_price($p_row->product, $p_row->qty);
}

edited Dec 29 '20 at 06:44

answered Dec 29 '20 at 06:38

Hammad Ahmed khan

1,618
7
19

Thanks.. Please have a look at my modified question `Is it the solution?` That works but do not sure if that is the way. – Code Lover Dec 29 '20 at 06:41
1

yeah it looks fine – Hammad Ahmed khan Dec 29 '20 at 06:44

score 0 · Answer 3 · answered Dec 29 '20 at 07:08

Since $p_row->total doesn't exist yet, define it instead of trying to adding to it. Simply change += to =.

foreach ($this->products as $p_row) {
    $this->data[ $p_row->group_id ][] = $p_row;
    $p_row->total = gs_get_product_qty_price($p_row->product, $p_row->qty);
}

When you use +=, PHP will first read the initial value of the property and adds to that value. But since the property doesn't exist, it tries to read from an undefined property, which will throw the warning you see. Changing to = defines and sets the value instead.

php foreach loop undefined property / index notice while setting value to stdclass property or array variable

Is it the solution?

3 Answers3