Uncaught TypeError: Unsupported operand types: string * string in

[tolgahanacar]

I'm pulling currency api with json_decode.

I can read the data properly, but it returns problems with multiplication.
Sample;
['USD']['sale'] * $value

The following code:

<?php
$value1 = $_POST['value1'] // var_dump: string
$value2 = $_POST['value2'] // var_dump: string or int

echo $value1 * $value2; // example 1 * 3

Resulted in this output:

Uncaught TypeError: Unsupported operand types: string * string in  
// Converting with intval doesn't work, it returns values ​​as 0.

But I expected this output instead:

3

PHP Version

PHP 8.0.1

Operating System

Microsoft Windows 10 Home [10.0.19043]

[iluuu1994]

One of your operands must not be a numeric string. Can you provide the post parameters you're supplying? Also, PHP 8.0.1 is an old patch, can you try on the latest PHP 8.0.14?

[tolgahanacar]

$currency = json_decode(file_get_contents('https://api.example.com/embed/currency.json'), true);

$value = $_POST['value']; // var_dump: string
$usd = $currency['USD']['sale']; // var_dump: string

echo $value * $usd; // output error

I also tried with PHP Version 8.1.0.

[tolgahanacar]

I tried this as a solution.

$value = intval($_POST['value']); // var_dump: int
$usd = intval($currency['USD']['sale']); // var_dump: int

echo $value * $usd; // output 0

[iluuu1994]

@tolgahanacar But can you provide the output of the two var_dump calls? The error you're describing usually occurs when one of the operands isn't a valid numeric string. For example:

$foo = 'asdf';
$bar = '3';
echo $foo * $bar;

https://3v4l.org/3jMvJ#v8.0.14

Thus it would be useful to know what these operands are in your case.

[tolgahanacar]

@iluuu1994

$foo = 'asdf';
$bar = '3';
echo $foo * $bar;

// PHP: 8.1.0
// Result: Uncaught TypeError: Unsupported operand types: string * string in

// This problem may give output in the values ​​we define, but it may cause problems in operations pulled with json or direct array operations. I've seen this issue on several forum pages, but couldn't find any solution.

[iluuu1994]

@tolgahanacar

$value = $_POST['value']; // var_dump: string
var_dump($value);
$usd = $currency['USD']['sale']; // var_dump: string
var_dump($usd);

echo $value * $usd;

Can you provide the output of this?

[tolgahanacar]

PHP 8.1.0

string(3) "13.6" string(1) "1"
Fatal error: Uncaught TypeError: Unsupported operand types: string * string in

[iluuu1994]

@tolgahanacar You cannot multiply these operands. What result would you expect "USD" * "1" to be? What exactly your application is supposed to do when the operands aren't what you expect them to be, only you can know.

$currency = json_decode(file_get_contents('https://api.example.com/embed/currency.json'), true);
$value = filter_var($_POST['value'], FILTER_VALIDATE_FLOAT);
$usd = filter_var($currency['USD']['sale'], FILTER_VALIDATE_FLOAT);

if ($value === false || $usd === false) {
    // Do something else
}

echo $value * $usd;