PHP - Ds Vector::map() Function

The PHP Ds\Vector::map() function is used to retrieve the result of applying a callback to each value of a vector. This function does not affect the current instance instead, it returns a new result.

The "callback" is a callable function that should return what the new value will be in the new vector.

Syntax

Following is the syntax of the PHP Ds\Vector::map() function −

public Ds\Vector::map(callable $callback): Ds\Vector

Parameters

Following is the parameter of this function −

• callback − A callable function applies to each value.

Following is the syntax of the callback function −

callback(mixed $value): mixed

Return value

This function returns the result of applying a callback function to each value in a vector.

Example 1

The following program demonstrates the usage of the PHP Ds\Vector::map() function −

<?php 
   $vector = new \Ds\Vector([1, 2, 3, 4, 5]);
   echo "The original vector: \n";
   print_r($vector);
   echo "The result of applying callback function: \n";
   print_r($vector->map(function($value) {  
      return $value * 5;  
   }));
?>

Output

After executing the above program the following output will be displayed −

The original vector:
Ds\Vector Object
(
    [0] => 1
    [1] => 2
    [2] => 3
    [3] => 4
    [4] => 5
)
The result of applying callback function:
Ds\Vector Object
(
    [0] => 5
    [1] => 10
    [2] => 15
    [3] => 20
    [4] => 25
)

Example 2

Following is another example of the PHP Ds\Vector::map() function. We use this function to retrieve the result by applying the callback function on each element of this vector ([5, 15, 25, 35, 45]) −

<?php 
   $vector = new \Ds\Vector([5, 15, 25, 35, 45]);
   echo "The original vector is: \n";
   print_r($vector);
   echo "The result of applying callback function: \n";
   var_dump($vector->map(function($value) {  
      return $value <= 30; 
   })); 
?>

Output

The above program produces the following output −

The original vector is:
Ds\Vector Object
(
    [0] => 5
    [1] => 15
    [2] => 25
    [3] => 35
    [4] => 45
)
The result of applying callback function:
object(Ds\Vector)#3 (5) {
  [0]=>
  bool(true)
  [1]=>
  bool(true)
  [2]=>
  bool(true)
  [3]=>
  bool(false)
  [4]=>
  bool(false)
}