PHP中的类型约束介绍

<?php
?
class Test
{
??? public function test_array(array $arr)
??? {
??????? print_r($arr);
??? }
?
??? public function test_class(Test1 $test1 = null)
??? {
??????? print_r($test1);
??? }
?
??? public function test_callable(callable $callback,$data)
??? {
??????? call_user_func($callback,$data);
??? }
?
??? public function test_interface(Traversable $iterator)
??? {
??????? print_r(get_class($iterator));
??? }
?
??? public function test_class_with_null(Test1 $test1 = NULL)
??? {
?
??? }
}
?
class Test1{}
?
$test = new Test();
?
//函数调用的参数与定义的参数类型不一致时,会抛出一个可捕获的致命错误.
?
$test->test_array(array(1));
$test->test_class(new Test1());
$test->test_callable('print_r',1);
$test->test_interface(new ArrayObject(array()));
$test->test_class_with_null();

$int? = new? SplInt ( 94 );
?
try {
???? $int? =? 'Try to cast a string value for fun' ;
} catch ( UnexpectedValueException $uve ) {
??? echo? $uve -> getMessage () .? PHP_EOL ;
}
?
echo? $int? .? PHP_EOL ;
/*
运行结果：
Value not an integer
94
*/