Array Operators in PHP : Tutorial

We can perform operations on arrays using Arrays Operators like Union, Equality, Identity, Inequality and Non-identity.

List of Array Operators

Name 			Syntax			Result
================================================================================
Union 			$array1  +  $array2	Union of $array1 and $array2.

Equality		$array1 ==  $array2	TRUE if $array1 and $array2 have the same key/value pairs.

Identity		$array1 === $array2	TRUE if $array1 and $array2 have the same key/value pairs 
				                in the same order and of the same types.
											
Inequality		$array1 !=  $array2	TRUE if $a is not equal to $b.

Inequality		$array1 <>  $array2	TRUE if $a is not equal to $b.

Non-identity    	$array1 !== $array2	TRUE if $a is not identical to $b.

Union Array Operator (+)

The Union operator (+) appends right-hand oparand (array) to the left-hand oparand (array).

If there are keys that exist in both arrays, then the elements from the left-hand array will be used, and the matching elements from the right-hand array will be ignored.

Example :

<?php

 $array1 = array("a" => "Java", "b" => "Objective-C", "c" => ".Net");
 $array2 = array( "a" => "Smalltalk","d" => "Pearl", "e" => "PHP");

 $union1 = $array1 + $array2; // Union of $array1 and $array2
 echo "Union of \$array1 and \$array2: <br>";
 var_dump($union1);

 $union2 = $array2 + $array1; // Union of $array2 and $array1
 echo "<br>Union of \$array2 and \$array1: <br>";
 var_dump($union2);

?>

Output
	

Union of $array1 and $array2: 
array(5) {
  ["a"]=> string(4) "Java"
  ["b"]=> string(11) "Objective-C" 
  ["c"]=> string(4) ".Net" 
  ["d"]=> string(5) "Pearl" 
  ["e"]=> string(3) "PHP"
} 
Union of $array2 and $array1: 
array(5) { 
  ["a"]=> string(9) "Smalltalk" 
  ["d"]=> string(5) "Pearl" 
  ["e"]=> string(3) "PHP" 
  ["b"]=> string(11) "Objective-C" 
  ["c"]=> string(4) ".Net" 
}

In the above example, key "a" in array1 has value "Java" where as array2 has the key "a" having value as "Smalltalk". Thus,result of array1 + array2 will have key "a" from the left-hand array and the right hand key "a" element will be ignored.

Equality Array Operator (==)

Equality Array Operator is used to check if both arrays have the same elements or not.

If array1 and array2 have the same elements (key value pairs) then boolean true is returned, else boolean false is returned.

Example :

<?php

$array1 = array("Java","Smalltalk","Objective-C","Perl");
$array2 = array("Java","Smalltalk","Objective-C","Perl");
$array3 = array("Java","Smalltalk","Objective-C","Perl",".Net");

echo var_dump($array1 == $array2) ."<br>";

echo var_dump($array2 == $array3) ."<br>";

?>

Output
	

bool(true)
bool(false)

Inequality Array Operator (!=)

Inequality Array Operator is used to check if both arrays have the same elements or not.

If array1 and array2 have do not have same elements (key value pairs) then boolean false is returned, else boolean true is returned.

Example :

<?php

$array1 = array("Java","Smalltalk","Objective-C","Perl");
$array2 = array("Java","Smalltalk","Objective-C","Perl");
$array3 = array("Java","Smalltalk","Objective-C","Perl",".Net");

echo var_dump($array1 != $array2) ."<br>";

echo var_dump($array2 != $array3) ."<br>";

?>

Output
	

bool(false)
bool(true)

Identity Array Operator (===)

Two arrays are Identical Only when the Keys and Values both are equal.



Example :

<?php

$array1 = array("PHP", "Java");
$array2 = array("1" => "Java", "0" => "PHP");


// == returns true 
echo var_dump($array1 == $array2) ."<br>";

// === returns false as keys are different
echo var_dump($array1 === $array2) ."<br>";

?>

Output
	

bool(true) 
bool(false) 

Non-identity Array Operator (!==)

Two arrays are Non-identity when the Keys and Values both are not equal.



Example :

<?php

$array1 = array("PHP", "Java");
$array2 = array("1" => "Java", "0" => "PHP");


// == returns false 
echo var_dump($array1 != $array2) ."<br>";

// === returns true as keys are different
echo var_dump($array1 !== $array2) ."<br>";

?>

Output
	

bool(false) 
bool(true)