Answer D is correct. Because PHP is automatically trying to convert the string
“0mydeviceid” to 0 when comparing it with the equal operator == , your condition
in answer B evaluates to true even though the user input is not a valid numeric
value.The expression in answer C, on the other hand, correctly determines that
the user input is not a valid integer—but that will always be the case because
you’re likely to always receive user input in the form of a string—so, even if that
string can be converted to an integer value, the identity test will fail.