PHP – Array Operators

PHP defines the following set of symbols to be used as operators on array data types −

The Union operator appends the right-hand array appended to left-hand array. If a key exists in both arrays, the elements from the left-hand array will be used, and the matching elements from the right-hand array will be ignored.

Example: Union Opeator in PHP

The following example shows how you can use the union operator in PHP −

<?php
   $arr1=array("phy"=>70, "che"=>80, "math"=>90);
   $arr2=array("Eng"=>70, "Bio"=>80,"CompSci"=>90);
   $arr3=$arr1+$arr2;
   var_dump($arr3);
?>

It will produce the following output −

array(6) {
   ["phy"]=>
   int(70)
   ["che"]=>
   int(80)
   ["math"]=>
   int(90)
   ["Eng"]=>
   int(70)
   ["Bio"]=>
   int(80)
   ["CompSci"]=>
   int(90)
}

Example: When Two Array are Equal

Two arrays are said to be equal if they have the same key-value pairs.

In the following example, we have an indexed array and other associative array with keys corresponding to index of elements in first. Hence, both are equal.

<?php
   $arr1=array(0=>70, 2=>80, 1=>90);
   $arr2=array(70,90,80);
   var_dump ($arr1==$arr2);
   var_dump ($arr2!=$arr1);
?>

It will produce the following output −

bool(true)
bool(false)

Example: When Two Arrays are Identical

Arrays are identical if and only if both of them have same set of key-value pairs and in same order.

<?php
   $arr1=array(0=>70, 1=>80, 2=>90);
   $arr2=array(70,90,80);
   var_dump ($arr1===$arr2);
   $arr3=[70,80,90];
   var_dump ($arr3===$arr1);
?>

It will produce the following output −

bool(false)
bool(true)