您可以使用json_decode函数将其转换为PHP对象，然后访问其属性。对于您的示例，您可以执行以下操作以获取“amount”属性：

<?php
$js='{"1":{"amount":"700","date":"2022-10-31","amount_discount":"0","amount_fine":"0","description":"","collected_by":"John Doe","payment_mode":"Cash","received_by":"12","inv_no":1},"2":{"amount":"300","date":"2022-12-17","description":" Paid by: Jane Doe","amount_discount":0,"amount_fine":"0","payment_mode":"upi","received_by":"23","inv_no":2}}';
echo json_decode($js)->{"1"}->amount;
?>

$data = json_decode('{"1":{"amount":"700","date":"2022-10-31","amount_discount":"0","amount_fine":"0","description":"","collected_by":"John Doe","payment_mode":"Cash","received_by":"12","inv_no":1},"2":{"amount":"300","date":"2022-12-17","description":" Paid by: Jane Doe","amount_discount":0,"amount_fine":"0","payment_mode":"upi","received_by":"23","inv_no":2}}');
Ex1: ((array) $data)[1]->amount
Ex2: $data->{'1'}->amount]);

试试这个

$json_string = '{"1":{"amount":"700","date":"2022-10-31","amount_discount":"0","amount_fine":"0","description":"","collected_by":"John Doe","payment_mode":"Cash","received_by":"12","inv_no":1},"2":{"amount":"300","date":"2022-12-17","description":" Paid by: Jane Doe","amount_discount":0,"amount_fine":"0","payment_mode":"upi","received_by":"23","inv_no":2}}';

$json_data = json_decode($json_string, TRUE);