Difference between “!==” and “==!” in PHP

!== Operator: It is called as non-identical operator. It returns true if operands are not equal, or they are not of the same type.

Syntax:

$x !== $y

Where $x and $y are the operands.



==! Operator: It is nothing but it can be further written as ==(!operand) which returns true or false depending on operands. Both the operators returns the boolean values either true or false.

Syntax:

$x ==! $y

Examples:

Input: $x = true
       $y = false
Operator: $x !== $y 
Output: true

Operator: $x ==! $y
Output: true

Example 1: This program uses both operands and returns the output.

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<?php
// PHP program to demonstrate
// !== and ==! operator
  
// Declare variables
$x = true;
$y = false;
$z = true;
  
// Using !== operator
echo "Using !== operator\n";
  
// Is $x not equals to $y
// so true returned
var_dump($x !== $y);
  
// Is $x not equals to $z
// so false returned
var_dump($x !== $z);
  
// Is $y not equals to $z
// so true returned
var_dump($y !== $z);
  
// Using ==! operator
echo "\nUsing ==! operator\n";
  
// Is $x equals to (!$y)
// so true returned
var_dump($x ==! $y);
  
// Is $x equals to (!$z)
// so false returned
var_dump($x ==! $z);
  
// Is $y equals to (!$z)
// so true returned
var_dump($y ==! $z);
  
?>

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Output:

Using !== operator
bool(true)
bool(false)
bool(true)

Using ==! operator
bool(true)
bool(false)
bool(true)

Program 2:

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<?php
// PHP program to demonstrate
// !== and ==! operator
  
// Dsclare associative array
$x = array(
    "1" => "Geeks"
    "2" => "for",
    "3" => "Geeks"
);
  
$y = array(
    "5" => "Tony",
    "6" => "Captain",
    "7" => "Thor"
);
  
// Union of $x and $y
$z = $x + $y
  
// Using !== operator
echo "Using !== operator\n";
  
// Is $x not equals to $y
// so true returned
var_dump($x !== $y);
  
// Is $x not equals to $z
// so true returned
var_dump($x !== $z);
  
// Is $y not equals to $z
// so true returned
var_dump($y !== $z);
  
// Using ==! operator
echo "\nUsing ==! operator\n";
  
// Is $x equals to (!$y)
// so false returned
var_dump($x ==! $y);
  
// Is $x equals to (!$z)
// so false returned
var_dump($x ==! $z);
  
// Is $y equals to (!$z)
// so false returned
var_dump($y ==! $z);
  
?>

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Output:

Using !== operator
bool(true)
bool(true)
bool(true)

Using ==! operator
bool(false)
bool(false)
bool(false)


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