I recently studied some code that I'm supposed to use for different reasons, it's unrelevant. The thing I've noticed is someone using the operator "===" which I can't make sense out of. I've tried it with a function and it corresponds in crazy ways. The language is PHP by the way.
Does anyone know what the definition of this operator is, I can't even find it in the declaration of php operators.
$a === $b (Identical) TRUE if $a is equal to $b, and they are of the same type. (introduced in PHP 4)
The triple equals sign === checks to see whether two variables are equal and of the same type.
$a == $b Equal TRUE if $a is equal to $b.
$a === $b Identical TRUE if $a is equal to $b, and they are of the same type.
> "5" == 5;
True
> "5" === 5;
False
See http://www.wellho.net/mouth/863_Double-and-Triple-equals-operator-in-PHP.html that i got for googling on "php three equals operator".
At one point it says that :
A double = sign is a comparison and tests whether the variable / expression / constant to the left has the same value as the variable / expression / constant to the right.
A triple = sign is a comparison to see whether two variables / expresions / constants are equal AND have the same type - i.e. both are strings or both are integers.
It also gives an example to explain it.
For PHP, there many different meanings a zero can take
So === is added to ensure the type and the value are the same.
in PHP you may compare 2 values using the == operator or === operator. the difference is this:
PHP is a dynamic, interpreted language that is not strict on data types. it means that the language itself will try to convert data types, whenever needed.
echo 4 + "2"; // output is 6
output is integer value 6. because + is numerical addition operator in PHP, so if you provide it operands with other data types, PHP will first convert them to their appropriate type ( "2" will be converted to 2 ) and then perform the operation.
if you use == as comparison operator with 2 operands that might be in different data types, PHP will convert the second operand type, to the first's. so:
4 == "4" // true
php converts "4" to 4, and then compares the values. in this case the result will be true.
if you use === as comparison operator, PHP will not try to convert any data types. so if the operands' types are different, then they are NOT identical.
4 === "4" // false
When you starting seeing anything repeated three times you know the guy typing has turrets.
You'll see this operator in many dynamically typed languages, not just PHP.
== will try to convert whatever it's dealing with into types that it can compare.
=== will strictly compare the type and value.
In any dynamically typed language you have to be careful with ==, you can get some interesting bugs.
The ternary === is less convenient, but it's safer. For comparisons you should always give some additional thought to whether it should be === or ==