Research on the variable scope of include files in PHP, _PHP tutorial

Research on variable scope of include files in php,

In php we sometimes need to include a file. For example, when I was writing a framework some time ago, I planned to use native PHP as the template, and then write a display method to introduce the template file, but this was just my imagination.

After writing it, I found that all variables in the template were undefined. Through various research and searching for information, I summarized the scope in several situations when including files.

The first case: A file includes B file, and the variables in A can be called in B file.

A file code :

<?<span>php
 </span><span>$aaa</span> = '123'<span>;
 
 </span><span>include</span> "B.php";

B file code:

<?<span>php

</span><span>echo</span> <span>$aaa</span>;

The content can be output normally.

Second case: File A includes file B, and then the variables of file B can be called in file A.

A file code :

<?<span>php

</span><span>include</span> "B.php"<span>;

</span><span>echo</span> <span>$fff</span>;

B file code :

<?<span>php

</span><span>$fff</span> = 'i am f';

At this time, the content can be output normally.

Third situation: File B is called in a method of a certain class in file A, and then the variables in the method can be called in file B.

A file code :

<?<span>php

</span><span>class</span><span> test{
    </span><span>public</span> <span>function</span><span> show(){
        </span><span>$bbb</span> = 'abc'<span>;
        </span><span>include</span> "B.php"<span>;
    }
}

</span><span>$t</span> = <span>new</span><span> test;
</span><span>$t</span>->show();

Code of file B:

<?<span>php

</span><span>echo</span> <span>$bbb</span>;

At this time, the content can be output normally.

Fourth case: File A imports file B through a defined function. Variables in A cannot be used in file B, but variables in the calling function (display) in file A can be used.

A file code:

<?<span>php
</span><span>$aaa</span> = '123'<span>;

</span><span>function</span> display(<span>$file</span><span>){
    </span><span>$bbb</span>= 'asdasdas'<span>;
    </span><span>include</span> <span>$file</span><span>;
}

display(</span>"B.php");

B file code:

<?<span>php
</span><span>echo</span> <span>$aaa</span><span>;
</span><span>echo</span> <span>$bbb</span>;

After running, $aaa prompts that it is undefined, and $bbb can be output normally.

Original link: http://www.cnblogs.com/dragondean/

So I started to assume that using a display method to introduce templates was not feasible. Based on the three situations, I finally chose to write a class to import the template file. Currently, ThinkPHP and Smarty also use classes to introduce template files. Any deficiencies in the article are welcome to be corrected.