Is there anyway to make it so that the following code still uses a switch and returns b not a? Thanks!
$var = 0;
switch($var) {
case NULL : return 'a'; break;
default : return 'b'; break;
}
Using if statements, of course, you'd do it like this:
$var = 0;
if($var === NULL) return 'a';
else return 'b';
But for more complex examples, this becomes verbose.
I think this article explains it pretty well:
Type-coercing comparison operators will convert numeric strings to numbers
Just to quote the main issue here:
According to php language.operators.comparison, the type-coercing comparison operators will coerce both operands to floats if they both look like numbers, even if they are both already strings:
where both strings are using exponential notation, hence are treated as numeric strings, making loose comparison (==), coerce these strings to floats before actually "loosely" comparing them.
As a best practice and to prevent unexpected behaviour, always try to use identity equality (===), especially when dealing with strings.
PHP compares sequentially (in the order of declaration) the object properties and stops at the first inequal property found. This behavior is not documented, so there's not much to be said about it, sadly, other than looking at the source of PHP.
Not documented is usually a synonym of "don't rely on it".
When you compare a string this way, it will go from left to right, and compare each character in the given string to see if they are different, until it finds a difference, then it will decide which string is bigger by comparing the ASCII value of this last character. Coincidentally, since you are using only numbers, the highest numbers are also higher on the ASCII table.
This solution will work as long as you use only numbers in your comparisons, and that each string has the same number of characters
Also note that this works only since you are using the YYYY-MM-DD format, if you used another format it would not work.
Conversion is when a value is, um, converted to a different type. The result is a value of the target type, and there are rules for what output value results from what input (of the source type).
For example:
int i = 3;
unsigned int j;
j = i; // the value of "i" is converted to "unsigned int".
The result is the unsigned int value that is equal to i modulo UINT_MAX+1, and this rule is part of the language. So, in this case the value (in English) is still "3", but it's an unsigned int value of 3, which is subtly different from a signed int value of 3.
Note that conversion happened automatically, we just used a signed int value in a position where an unsigned int value is required, and the language defines what that means without us actually saying that we're converting. That's called an "implicit conversion".
"Casting" is an explicit conversion.
For example:
unsigned int k = (unsigned int)i;
long l = long(i);
unsigned int m = static_cast<unsigned int>(i);
are all casts. Specifically, according to 5.4/2 of the standard, k uses a cast-expression, and according to 5.2.3/1, l uses an equivalent thing (except that I've used a different type). m uses a "type conversion operator" (static_cast), but other parts of the standard refer to those as "casts" too.
User-defined types can define "conversion functions" which provide specific rules for converting your type to another type, and single-arg constructors are used in conversions too:
struct Foo {
int a;
Foo(int b) : a(b) {} // single-arg constructor
Foo(int b, int c) : a(b+c) {} // two-arg constructor
operator float () { return float(a); } // conversion function
};
Foo f(3,4); // two-arg constructor
f = static_cast<Foo>(4); // conversion: single-arg constructor is called
float g = f; // conversion: conversion function is called
Sorry, you cannot use a
===comparison in a switch statement, since according to the switch() documentation:This means you'll have to come up with a workaround. From the loose comparisons table, you could make use of the fact that
NULL == "0"is false by type casting:Live Demo