PHP方法的返回值示例详解

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

var_dump(testA(1, 2)); // NULL

function testB($a, $b)
{
 return $a + $b;
}

var_dump(testB(1, 2)); // 3

function testC($a, $b)
{
 return;
 echo $a + $b; // 后面不会执行了
}

var_dump(testC(1, 2)); // NULL

function testD($a, $b)
{
 return [
  $a + $b,
  $a * $b,
 ];
}

var_dump(testD(1, 2)); // [3, 2]

function testE($a, $b) : bool
{
 if($a+$b == 3){
  return TRUE;
 }else{
  return NULL;
 }
}

var_dump(testE(1, 2)); // true
var_dump(testE(1.1, 2.2)); //TypeError: Return value of testE() must be of the type bool, null returned

function testF($a, $b): array
{
 return [
  $a + $b,
  $a * $b,
 ];
}
var_dump(testF(1, 2)); // [3, 2]

interface iA{

}
class A implements iA
{}
class B extends A
{
 public $b = 'call me B!';
}

function testG(): A
{
 return new B();
}

function testH(): B
{
 return new B();
}

function testI(): iA
{
 return new B();
}

var_dump(testG()); // B的实例
var_dump(testH()); // B的实例
var_dump(testI()); // B的实例

function testJ(): void
{
 echo "testJ";
 // return 1;
}
var_dump(testJ());