How to fix Fatal error: Uncaught TypeError: Unsupported operand types: string string [PHP] [HTML]-CodePudding

so hopefully i ask my question in the proper manner. I am trying to code a calculator that will display an error when someone tries to fill in a letterinstead of a number. How do i get this to work without a "Fatal error: Uncaught TypeError: Unsupported operand types: string string" stopping the code. And then the Exception should be shown next to the input field.

I add a screenshot of the result i am trying to get and i will give the code i have sofar.[

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Calculator</title>
</head>

<?php

$number1 = "";
$number2 = "";
$result = "";
$calculate = "";

if (isset($_GET['calculate'])) {
    $number1 = $_GET['number1'];
    $number2 = $_GET['number2'];
    $calculate = $_GET['calculate'];

    function isValidNumber1($number1)
    {
        if (!is_numeric($number1)) {
            throw new Exception("Number 1 is not a number!");
        }
    }
    try {
        isValidNumber1($number1);
        $result = $number1   $number2;
    } catch (Exception $e) {
        echo $e->getMessage() . PHP_EOL;
    }


    switch ($calculate) {
        case "Add":
            $result = $number1   $number2;
            break;
        case "Substract":
            $result = $number1 - $number2;
            break;
        case "Multiply":
            $result = $number1 * $number2;
            break;
        case "Divide":
            $result = $number1 / $number2;
            break;
        case "Modulo":
            $result = $number1 % $number2;
            break;
    }
}

?>

<body>
    <h1>Calculator</h1>

    <form action="" method="get" id="calculator">

        <label for="number1">Number 1:</label>
        <input type="text" name="number1" value="<?php echo $number1; ?>"><br><br>
        <label for=" number2">Number 2:</label>
        <input type="text" name="number2" value="<?php echo $number2; ?>"><br><br>

        <?php
        echo "<p>Operation:  $calculate</p>";
        echo "<p>Result: $result</p>";
        ?>

        <div>
            <input type="submit" name="calculate" value="Add">
            <input type="submit" name="calculate" value="Substract">
            <input type="submit" name="calculate" value="Multiply">
            <input type="submit" name="calculate" value="Divide">
            <input type="submit" name="calculate" value="Modulo">
        </div>
    </form>

</body>

</html>

][1]

CodePudding user response：

to fix the current implementation

you need to add the switch statements inside the try block,
so when the validation exception fire it will escape running it
and about showing the error beside the input you can set the exception message in a variable and print it beside the input " ,

your implementation after those edits will looks like :

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Calculator</title>
</head>

<?php

$number1 = "";
$number2 = "";
$result = "";
$calculate = "";
$number1Error = '';

if (isset($_GET['calculate'])) {
    $number1 = $_GET['number1'];
    $number2 = $_GET['number2'];
    $calculate = $_GET['calculate'];
    $errors = [];
    
    function isValidNumber1($number1)
    {
        if (!is_numeric($number1)) {
            throw new Exception("Number 1 is not a number!");
        }
    }
    
    
    try {
        isValidNumber1($number1);
        $result = $number1   $number2;
        
        switch ($calculate) {
        case "Add":
        var_dump($number1);
            $result = $number1   $number2;
            break;
        case "Substract":
            $result = $number1 - $number2;
            break;
        case "Multiply":
            $result = $number1 * $number2;
            break;
        case "Divide":
            $result = $number1 / $number2;
            break;
        case "Modulo":
            $result = $number1 % $number2;
            break;
    }
    
    } catch (Exception $e) {
        $number1Error = $e->getMessage() . PHP_EOL;
        
    }


    
}

?>

<body>
    <h1>Calculator</h1>

    <form action="" method="get" id="calculator">

        <label for="number1">Number 1: </label>
        <input type="text" name="number1" value="<?php echo $number1; ?>"> <?php echo $number1Error; ?><br><br>
        <label for=" number2">Number 2:</label>
        <input type="text" name="number2" value="<?php echo $number2; ?>"><br><br>

        <?php
        echo "<p>Operation:  $calculate</p>";
        echo "<p>Result: $result</p>";
        ?>

        <div>
            <input type="submit" name="calculate" value="Add">
            <input type="submit" name="calculate" value="Substract">
            <input type="submit" name="calculate" value="Multiply">
            <input type="submit" name="calculate" value="Divide">
            <input type="submit" name="calculate" value="Modulo">
        </div>
    </form>

</body>

</html>