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php 类型约束

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Release： 2016-06-23 14:32:37
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PHP 5 可以使用类型约束。函数的参数可以指定只能为对象（在函数原型里面指定类的名字），php 5.1 之后也可以指定只能为数组。 注意，即使使用了类型约束，如果使用NULL作为参数的默认值，那么在调用函数的时候依然可以使用NULL作为实参。

类型约束只支持对象 和 数组（php 5.1之后）两种类型。而不支持整型 和 字符串类型。

错误使用字符串类型约束会导致类似以下错误：

Catchable fatal error: Argument 1 passed to Models_Workflow_Instance::getRand() must be an instance of string, string given,
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详例：http://us3.php.net/manual/zh/language.oop5.typehinting.php

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