What does "===" mean?

$a === $b     (Identical)      

TRUE if $a is equal to $b, and they are of the same type. (introduced in PHP 4)

PHP Docs

http://www.php.net/ternary

$a == $b Equal TRUE if $a is equal to $b, except for (True == -1) which is still True.

$a === $b Identical TRUE if $a is equal to $b, and they are of the same type.

> "5" == 5;
True
> "5" === 5;
False

You can read here, short summary:

$a == $b Equal TRUE if $a is equal to $b after type juggling.

$a === $b Identical TRUE if $a is equal to $b, and they are of the same type.

In PHP you may compare two 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

The output is integer value 6, because + is the numerical addition operator in PHP, so if you provide operands with other data types to it, PHP will first convert them to their appropriate type ("2" will be converted to 2) and then perform the operation.

If you use == as the comparison operator with two 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 the 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

The triple equals sign === checks to see whether two variables are equal and of the same type.

See Double and Triple equals operator in PHP 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

1. it can be a Boolean false
2. it could be a null value
3. It could really be a zero

So === is added to ensure the type and the value are the same.

"===" matching the value in the variable as well as data type of the variable.