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PHP | Ds\Sequence reduce() Function

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The Ds\Sequence::reduce() function is an inbuilt function in PHP which is used to reduce the sequence to a single value using a callback function.


mixed abstract public Ds\Sequence::reduce ( callable $callback 
[, mixed $initial ] )

Parameters: This function accepts two parameters as mentioned above and described below:

  • $callback: This parameter holds the function which contains the operation on the elements and store carry. This callback function contains two arguments, carry and value, where carry is the value returned by the function and value is the value of element at the current iteration.
  • $initial: This parameter holds the initial value of carry, which can be NULL.

Return value: This function returns the final value of callback function.

Below programs illustrate the Ds\Sequence::reduce() function in PHP:

Program 1:

// Declare new sequence
$seq = new \Ds\Vector([1, 2, 3, 4, 5]); 
echo("Sequence Elements\n"); 
// Callback function with reduce function 
echo("\nElement after performing operation\n"); 
var_dump($seq->reduce(function($carry, $element) { 
    return $carry + $element + 2; 


Sequence Elements
Ds\Vector Object
    [0] => 1
    [1] => 2
    [2] => 3
    [3] => 4
    [4] => 5

Element after performing operation

Program 2:

// Declare new sequence
$seq = new \Ds\Vector([10, 20, 30, 40, 50]); 
echo("Original sequence elements\n"); 
$func_gfg = function($carry, $element) { 
    return $carry * $element
echo("\nSequence after reducing to single element\n"); 
// Use reduce() function 
var_dump($seq->reduce($func_gfg, 10)); 


Original sequence elements
Ds\Vector Object
    [0] => 10
    [1] => 20
    [2] => 30
    [3] => 40
    [4] => 50

Sequence after reducing to single element


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Last Updated : 22 Aug, 2019
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