What are common mistakes beginners make when creating a PHP calculator?

One common mistake beginners make when creating a PHP calculator is not properly sanitizing user input. This can lead to security vulnerabilities such as SQL injection or cross-site scripting attacks. To solve this issue, always validate and sanitize user input before using it in calculations. 

// Sanitize user input by using filter_input to ensure it is a valid number
$num1 = filter_input(INPUT_POST, 'num1', FILTER_VALIDATE_FLOAT);
$num2 = filter_input(INPUT_POST, 'num2', FILTER_VALIDATE_FLOAT);

// Perform calculations only if both numbers are valid
if ($num1 !== false && $num2 !== false) {
    $result = $num1 + $num2;
    echo "Result: $result";
} else {
    echo "Invalid input. Please enter valid numbers.";
}

Keywords

syntax errors variable naming operator precedence input validation error handling

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