Question

So I’ve been actively programming bot in school and work the past 5 years, but I never tried to find out the difference between == and ===.

I can see the difference of a comparator using a single =, it’ll look at the value of the left handed variable through the loop, ex:

while($line = getrow(something))

So what’s the difference between == and === in statements such as:

if ($var1 === $var2)
//versus
if ($var1 ==  $var2)

Likewise:

if ($var1 !== $var2)
//versus
if ($var1 != $var2)

I have always used double equals, I have never used tripple.
The languages I use are :php, vb.net, java, javascript, c/c++.

I’m interested in learning systematically what is going on in a tripple quote that is different than that of a double quote.

When should one be used over another? Thanks for appeasing to my curiosity 🙂

Answer 1

Typically, == looks at equality of value only. So, for instance…

5 == 5.0  //true

However, === also considers value and type (in the languages I am familiar with).

var five = 5;
var five_float = (float)5.0;

five === 5;        //true - both int, both equal to 5
five_float === 5;  //false - both equal 5 but one is an int and one is a float

FYI, the = operator (usually called the assignment operator) is used to set the value of the left side parameter to the right side. This is pretty obvious. However, in most languages, this will also return true if the assignment is successful. You want to avoid using = where you mean to use == (or ===) because it will look like a comparison, but it’s not – and it will return true unexpectedly.

For instance, lets say you want to check if a number is equal to 10…

myNumber = 7;
if(myNumber = 10)
{
    //will always be true and execute this code because myNumber will successfully
    //be assigned the value of 10 instead of checking to see if the number is 10.
    //oops!
}

A final note – this is true in PHP and JavaScript. I don’t think there is a === operator in C++ or Java and == has a slightly different meaning as well.