Convert a string to a number? How to solve

Convert a string to a number ??? Today, I encountered a strange phenomenon. it is very likely that I have not enough reserves. a problem occurs when the string of a number containing quotation marks is converted to a number. "1000", "902865066306 ", "02865066306", "SIP & nbsp; Phone", "IP & nbsp; Trunk", "", "trunk20", "ON2OFF", string converted into numbers ???
Today, I encountered a strange phenomenon. it is very likely that I have not enough reserves. a problem occurs when the string containing the quotation marks is converted to a number.

"1000","902865066306","02865066306","SIP Phone","IP Trunk","","trunk20","ON2OFF","1333230069","1333230072","1333230134","65","62","Connected"

The above is a piece of data, and the next operation

$arr = '"1000","902865066306","02865066306","SIP Phone","IP Trunk","","trunk20","ON2OFF","1333230069","1333230072","1333230134","65","62","Connected"';
$arr = explode(',',$arr);
print_r($arr);

Print

Array
(
    [0] => "1000"
    [1] => "902865066306"
    [2] => "02865066306"
    [3] => "SIP Phone"
    [4] => "IP Trunk"
    [5] => ""
    [6] => "trunk20"
    [7] => "ON2OFF"
    [8] => "1333230069"
    [9] => "1333230072"
    [10] => "1333230134"
    [11] => "65"
    [12] => "62"
    [13] => "Connected"
)

I want to compare the ninth character in the array with other data. when I convert the string enclosed by quotation marks into numbers, it is okay to add 0 to the back. However, today is different.

Echo $ arr [8] + 0; // The result is 0.

I was wondering, why is it 0? $ arr [8] clearly has a value, so I tested it again.

$num = "1333230069";
echo $num+0;//1333230069

After a long time, I didn't understand what was going on. then I used two methods to solve the problem. one was to use regular expressions to propose numbers, the other is to replace all double quotation marks in the string with null at the beginning.

But the doubt has not been solved. until now, I am wondering why the above practice produces 0 results rather than the expected number.

------ Solution --------------------
Var_dump ($ arr [8]); // string (12) "" 1333230069 ""
Var_dump ($ num); // string (10) "1333230069"

In this way, we can clearly understand that the double quotation marks at the beginning and end of $ arr [8] are removed before the operation.
------ Solution --------------------
$ A = str_getcsv ($ arr );
Var_dump ($ a [8]);


------ Solution --------------------
Based on the information you provided, I also tested it myself:

 $arr= Array
(0 => "1000",
    1 => "902865066306",
    2 => "02865066306",
    3 => "SIP Phone",
    4 => "IP Trunk",
    5 => "",
    6 => "trunk20",
    7 => "ON2OFF",
    8 => "1333230069",
    9 => "1333230072",
    10 => "1333230134",
    11 => "65",
    12 => "62",
    13 => "Connected"
);
echo gettype($arr[8])."
";
echo $arr[8]."
";
$str1=$arr[8]+0;
echo gettype($str1)."
";
echo ($str1)."
";

$num = "1333230069";
$num1=($num+0);
echo gettype($num)."
";
echo gettype($num1)."
";
echo $num1;

?>

The output result is:
String
1333230069
Integer
1333230069
String
Integer
1333230069

No problem was found.
------ Solution --------------------
Isn't it necessary to be so troublesome?

$arr = '"1000","902865066306","02865066306","SIP Phone","IP Trunk","","trunk20","ON2OFF","1333230069","1333230072","1333230134","65","62","Connected"';