PHP类的有关问题
PHP类的问题
在上面的类 PHP引擎是什么解析的呢？ 不是从上而下解析代码的吗？ 还没读到 class 之前已经开始实例化 这个class了？
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php 执行是分两个阶段进行的：
1、文法检查阶段
2、执行阶段
所以在同一程序文件中，类、函数的声明和使用没有先后之分
定义若如在嵌入文件中，就必须先嵌入，后使用
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执行的时候优先加载 类 函数 require include等，加载完了才会开始执行
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在同一程序文件中，类、函数的声明和使用没有先后之分。
include 文件才需要分先后。
------解决思路----------------------
当程序执行到实例化类时候就会自动在当前脚本中寻找所要实例化的类，如果被实例化的类是由require include而来的话，那么就需要写在实例化之前了
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