#    
## PHP functions
PHP has more than a thousand inbuilt functions and enables its developers to create their own functions as well. **Functions** are considered one of the extraordinary strengths of PHP; they are a structure of code that can be used repetitively. They need to be called in order to achieve their specific task. 
 

#   
## How to create a function in PHP
Below, we see how to create a function, `callEducative(),` which prints `Welcome to Educative!`.

<?php
function callEducative() {
  echo "Welcome to Educative!";
}

callEducative(); // function call
?>

# 
## Ds\Set `reduce()` function
This is an inbuilt function that applies operation using the callback function to reduce the set to a single value.

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

# 
## Code Example
The following code shows the implementation `reduce()` function:

<?php 
  

$set = new \Ds\Set([10, 15, 25, 35, 40]); 
  
echo("Initial elements of the set\n"); 
  
print_r($set); 
  
$f = function($carry, $element) { 
    return $carry * $element; 
}; 
  
echo("\nReduced to a single element\n"); 
  
// reduce() 
var_dump($set->reduce($f, 10)); 
  
?> 

# 
## Output





```txt
Initial elements of the set
Ds\Set Object
{
    [0] => 10
    [1] => 15
    [2] => 25
    [3] => 35
    [4] => 40
    
}

Reduced to a single element
int(5250000)

```

What is the Ds\Set reduce() function in PHP?

Ds\Set reduce() in PHP applies a callback operation to reduce a set to a single value.