What do !== and === mean in PHP? [duplicate]

Question

Possible Duplicates:
How do the equality (== double equals) and identity (=== triple equals) comparison operators differ?
Reference - What does this symbol mean in PHP?
php not equal to != and !==

What are the !== and === operators in this code snippet?

if ( $a !== null ) // do something
if ( $b === $a ) // do something

Answer 1

They are identity equivalence operators.

1 == 1
1 == "1"
1 === 1
1 !== "1"
true === true
true !== "true"
true == "true"

All of these equate to true. Also check this link provided by @mbeckish

Answer 2

They are strict type comparison operators. They not only check the value but also the type.

Consider a situation when you compare numbers or strings:

if (4 === 4) // same value and type
{
  // true
}

but

if (4 == "4") // same value and different type but == used
{
  // true
}

and

if (4 === "4") // same value but different type
{
  // false
}

This applies to objects as well as arrays.

So in above cases, you have to make sensible choice whether to use == or ===

It is good idea to use === when you are sure about the type as well

More Info:

• http://php.net/manual/en/types.comparisons.php

Answer 3

=== also checks for the type of the variable.

For instance, "1" == 1 returns true but "1" === 1 returns false. It's particularly useful for fonctions that may return 0 or False (strpos for instance).

This wouldn't work correctly because strpos returns 0 and 0 == false

if (strpos('hello', 'hello world!'))

This, however, would work :

if (strpos('hello', 'hello world!') !== false)