PHP：用字符串计算可靠

Question

In PHP I make a simple calculation, but with strings

$num_1 = '200.50'; (string)
$num_2 = '100.50'; (string)

echo $num_1 - $num_2

The result is as expected 100.00

What I wonder about is the fact that I did not cast the values to float and still got the correct result.
And my question is if this kind of (string) calculation is reliable ?

Answer 1

It's reliable if you use numbers in your string. If you use alphabet characters, special characters, or other things you wouldn't expect in basic maths, you may get unexpected results.

To learn more about what behavior you can expect and how to prevent issues, see the PHP docs for type juggling.

http://php.net/manual/en/language.types.type-juggling.php