CakePhp supports functional programming. Functional Programming in CakePhp is a criterion as are crucial, logical and Object Oreinted programming. In CakePhp everything resides inside a function, in the mathematical sense. The
consequence of that you will not face any side effect since everthing depends merely on the input of the function. It means that you cannot have any inconsistent state, once you compute something, you cannot  change it to something else.

Function in Php

Functions are important part in the Php 

// Function which are used as a variable
$func = function() {
  return 42;
};
 
// Function which are used as a return type
function createFunction() {
  return function() { return "Thanks"; };
};
$func2 = createFunction();
 
// Function as a parameter
function display($func) {
  echo $func()."\n\n";
}
 
// Call a function by name
call_user_func_array('strtoupper', $someString);
 
// objects as functions
class SomeClass {
public function __invoke($param1, $param2) {
[...]
}
}
$instance = new SomeClass();
$instance('First', 'Second'); // call the __invoke() method

Mapping

After creating the functions we will do the mapping between the functions. We manipulate the array using mapping.

// The crucial way :
 
foreach($stringArray as $k => $v) {
  $stringArray[$k] = strtoupper($v);
}
// The functional way :
 
$result = array_map('strtoupper', $stringArray);

Reducing

Reducing an array, sometimes called “fold” in functional languages :

// The crucial way :
 
$result = 0;
foreach($intArray as $v) {
  $result += $v;
}
// The functional way :
 
$result = array_reduce($intArray, function($a, $b) { return $a + $b; }, 0)

Filtering

Filtering is used to filter the array

// The crucail way :
 
$result = array();
foreach($intArray as $v) {
  if($v % 2 === 0) {
    $result[] = $v;
  }
}
// The functional way :
 
$result = array_filter($intArray, function($a) { return ($a % 2 === 0); })