PHP - Ds Map::intersect() Function

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The PHP Ds\Map::intersect() function is used to create a new map by intersecting keys with another map. The term "intersecting keys" refers to the common keys in both maps.

The newly created map contains the key-value pairs from the current instance whose keys are present in another map. In other words, it returns a copy of the current instance with all keys removed that are not present in the other map.

Syntax

Following is the syntax of the PHP Ds\Map::intersect() function −

public Ds\Map::intersect(Ds\Map $map): Ds\Map

Parameters

Following is the parameter of this function −

• map − The other map contains the keys to intersect with.

Return value

This function returns a key intersection of the current instance and another map.

Example 1

The following is the basic example of the PHP Ds\Map::intersect() function −

<?php  
   $map1 = new \Ds\Map(["1" => 10, "2" => 20, "4" => 40]);
   echo "The map1 elements are: \n";
   print_r($map1);
   $map2 = new \Ds\Map(["2" => 20, "4" => 40, "5" => 50]);
   echo "The map2 elements are: \n";
   print_r($map2);
   echo "The intersection of map1 and map2 is: \n";
   #using intersect() function
   print_r($map1->intersect($map2));
?>

Output

The above program produces the following output −

The map1 elements are:
Ds\Map Object
(
    [0] => Ds\Pair Object
        (
            [key] => 1
            [value] => 10
        )

    [1] => Ds\Pair Object
        (
            [key] => 2
            [value] => 20
        )

    [2] => Ds\Pair Object
        (
            [key] => 4
            [value] => 40
        )

)
The map2 elements are:
Ds\Map Object
(
    [0] => Ds\Pair Object
        (
            [key] => 2
            [value] => 20
        )

    [1] => Ds\Pair Object
        (
            [key] => 4
            [value] => 40
        )

    [2] => Ds\Pair Object
        (
            [key] => 5
            [value] => 50
        )

)
The intersection of map1 and map2 is:
Ds\Map Object
(
    [0] => Ds\Pair Object
        (
            [key] => 2
            [value] => 20
        )

    [1] => Ds\Pair Object
        (
            [key] => 4
            [value] => 40
        )

)

Example 2

If no keys are common in the given maps, the intersection of both maps will be empty ().

Following is another example of the PHP Ds\Map::intersect() function. We use this function to create a new map by intersecting keys with this map (["4" => "Point", "5" => "India"]) −

<?php  
   $map1 = new \Ds\Map(["1" => "Tutorials", "2" => "Point", "3" => "India"]); 
   echo "The map1 elements are: \n";
   foreach($map1 as $key=>$value){
	   echo "[".$key."] = ".$value."\n";
   }
   $map2 = new \Ds\Map(["4" => "Point", "5" => "India"]);
   echo "\nThe map2 elements are: \n";
   foreach($map2 as $key=>$value){
	   echo "[".$key."] = ".$value."\n";
   }
   echo "The intersection of map1 and map2 is: \n";
   #using intersect() function
   $new_map = $map1->intersect($map2);
   print_r($new_map);
?>  

Output

After executing the above program, it will display the following output −

The map1 elements are:
[1] = Tutorials
[2] = Point
[3] = India

The map2 elements are:
[4] = Point
[5] = India
The intersection of map1 and map2 is:
Ds\Map Object
(
)

Example 3

In the example below, we use this Ds\Map::intersect() function to create a new map by intersecting keys with another map.

<?php  
   $map1 = new \Ds\Map([1 => 'a', 2 => 'e', 3 => 'i']); 
   echo "The map1 elements are: \n";
   foreach($map1 as $key=>$value){
	   echo "[".$key."] = ".$value."\n";
   }
   $map2 = new \Ds\Map([3 => 'o', 4 => 'u']);
   echo "\nThe map2 elements are: \n";
   foreach($map2 as $key=>$value){
	   echo "[".$key."] = ".$value."\n";
   }
   echo "The intersection of map1 and map2 is: \n";
   #using intersect() function
   $new_map = $map1->intersect($map2);
   print_r($new_map);
?>

Output

Once the above program is executed, the following output will be displayed:

The map1 elements are:
[1] = a
[2] = e
[3] = i

The map2 elements are:
[3] = o
[4] = u
The intersection of map1 and map2 is:
Ds\Map Object
(
    [0] => Ds\Pair Object
        (
            [key] => 3
            [value] => i
        )

)