php中的关联数组值+=

Question

I have an Invoice items list. I create a tax breakup array (associative array) to store unique tax percentages and their tax amount.

$taxbreakup=array(); 
@foreach($invoiceinfo->invoiceitems as $invoice_items)
    $taxbreakup[$invoice_items->tax_percentage]+=$invoice_items->tax_amount;
@endforeach

Group Tax percentage and display total tax amount for particular tax percentage

@foreach($taxbreakup as $key => $value)
 
 <tr>

  <td colspan="12"></td>
  <td class="btmlft" colspan="2">GST ({{number_format($key,2)}})%</td>
  <td class="btmlft rghtbrd alignright">{{number_format(($value),2) }}</td>
  </tr>
 
 @endforeach

I got an undefined index error.

Answer 1

In order to use += the variable you are accumulating the result into must be initialized, in your case it does not yet exist and is not initialized.

Even if you wanted to do

$arr['val'] = $arr['val'] + 1;

the receiving variable need to have been created.

So I would use

$taxbreakup=array(); 
@foreach($invoiceinfo->invoiceitems as $invoice_items)
    // check accumulator exists before using it
    if ( ! isset($taxbreakup[$invoice_items->tax_percentage]) ) {
        $taxbreakup[$invoice_items->tax_percentage] = 0; 
    }
    $taxbreakup[$invoice_items->tax_percentage] += $invoice_items->tax_amount;
@endforeach
if ( ! isset($arr['hello']) ) { $arr['hello'] = 0; }

Answer 2

我认为这个变量 $taxbreakup 为空，检查 $taxbreakup 为空，然后执行 foreach