php_interested_func_things.md

Alternate Null Type Syntax

<?php

function myFunc(?MyObject $myObj) {
  echo 'Hello World!';
}

myFunc(null); // this is allowed
myFunc(); // this produces a fatal error: Too few arguments

Variadics

<?php
  
function myFunc($required, $optional = NULL, ...$variadicParams) {
  print_r($variadicParams);
}
  
myFunc(1, 2, 3, 4); // array([0] => 3, [1] => 4);

Return Type Declarations

<?php

function getFullName(string $firstName, string $lastName): string {
  return 100;
}

$name = getFullName('Serhii', 'Puchkovskyi');
echo gettype($name); // string

Return Void

If the function is going to return NULL, we can specify that it will return "void":

<?php

function myFunc(): void {
  echo 'Hello World!';
}

sayWorld(); // Hello World!

Lambda and Closure

<?php

$lambda = function($a, $b) {
  echo $a + $b;
};

$lambda(2, 3); // 5
echo (int) is_callable($lambda); // 1
echo get_class($lambda); // Closure

$string = 'Hello World!';
$closure = function() use ($string) {
  echo $string;
};
$closure(); // Hello World!

Early and Late Binding

<?php

$a = 'Some string';
// Early binding (default).
$b = function() use ($a) {
  echo $a;
};

$a = 'Hello World!';
$b(); // Some string

<?php

$a = 'Some string';
// Late binding (reference).
$b = function() use (&$a) {
  echo $a;
};

$a = 'Hello World!';
$b(); // Hello World!

Binding Closures to Scopes

<?php

class test {
  protected $text = 'Default text';

  public function showText() {
    return function () { return $this->text; };
  }
}

class testA extends test {}
class testB {
  protected $text = 'Some another text';
}
  
$testA = new testA();
$testB = new testB();
  
$test1 = $testA->showText()->bindTo($testB);
$test2 = Closure::bind($testA->showText(), $testB);
  
print_r($test1); // Some another text
print_r($test2); // Some another text

Self-Executing Closures

<?php
// Displays 'Hello World!'.
(function() {
  echo 'Hello World!';
})();

Helpful links:

• RFC: Lambda functions and closures
• Difference between closure parameters and the use keyword