This extension aims at helping people making PHP a stronger typed language and can be a good alternative to scalar type hinting. It provides different typehandling classes as such as integer, float, bool, enum and string
此扩展是实验性 的。 此扩展的表象，包括其函数名称以及其他此扩展的相关文档都可能在未来的 PHP 发布版本中未通知就被修改。使用本扩展风险自担 。
Tom (2009-10-28 08:34:57)
For your information, here is another work-around for this issue, that even works with PHP4 (in case you need to be compatible):
<?php
/**
* @param string $foo
*/
function foo($foo)
{
assert('is_string($foo); // Invalid argument type');
// do some foo
}
?>
This single-line of code should fix it for most people. It will throw an error whenever the expression evaluates to false (if $foo is not a string).
Most errors concerning scalar types are found during development or unit-testing. PHPUnit is fine with these and reports failed assertions as failed tests, also presenting the included message.
Note that assertions need to be turned on for this to work. See the manual page on assertions for more details.
Note that you may deactivate the checks on the target machine, so this comes without any performance penalty. So don't hesitate to make extensive use of this PHP-feature.
Note though: DON'T RELY ON ASSERTIONS FOR CHECKING USER INPUT!
In that case you may want to try this code:
is_string($foo) || trigger_error('String expected', E_USER_ERROR);
Or: simply throw an exception (as usual).
tom (2009-10-28 08:09:43)
For backwards compatibility issues:
We do know that auto-unboxing works for strings, thanks to the __toString() magic function. Auto-unboxing for other scalar types may be tricky but possible, by using the same function with another return type (which of cause has some limitations).
However auto-boxing is a real challenge.
If you can provide any details, I would appreciate that.
For auto-unboxing see this code-fragment:
<?php
class MyString {
private $value = "";
public function __construct($string) {
if (!is_string($string)) {
throw new InvalidArgumentException();
}
$this->value = $string;
}
public function __toString() {
return $this->value;
}
}
?>
For other scalar types, all that changes is the constructor function. Anything else remains unchanged. (While you are at it, you may want to add some type conversion functions for your personal convenience.)
HowTo:
<?php
function foo(MyString $string)
{
print "$string"; // auto-unboxing in action
}
// prints "Hello World!"
foo(new MyString("Hello World!"));
?>