What is the issue with adding two strings in PHP and why does it result in scientific notation?

When adding two strings in PHP, PHP will try to convert the strings to numbers and perform the addition operation. If the strings contain numerical values in scientific notation (e.g. "1.23e4"), PHP will interpret them as floating-point numbers and perform the addition accordingly. This can result in the final sum being displayed in scientific notation. To prevent PHP from converting the strings to numbers and displaying the result in scientific notation, you can use the `bcadd()` function from the BCMath extension. This function allows for arbitrary precision arithmetic and can handle string addition without converting to scientific notation.

$num1 = "1.23e4";
$num2 = "5.67e3";

$result = bcadd($num1, $num2, 2);

echo $result; // Outputs: 12356.70