类变量不停留（PHP）

Question

Alright, I'm not sure exactly 100% what's going on here, but I think it has to do with the fact that I'm trying to include a class using php's "include($file)" function.

the function import looks like this:

<?php
function import($file) {
    global $imported; $imported = true;
    $home_dir = "C:/xampp/htdocs/includes/";
    if (file_exists($home_dir.$file.".php")) {
        include_once($home_dir.$file.".php");
        }
    $imported = false;
    }
?>

All I do is call the following php in my index.php file:

<?php
import("php.buffer");

$out = new StringBuffer;
$out->write("test?");
echo "'".($out->get())."' &lt;- Buffer String Should Be Here";
?>

The php.buffer.php file looks like this:

<?php
class StringBuffer {
    public $buffer = "";

    public function set($string) {
        if (!isset($buffer)) { $buffer = ""; }
        $buffer = $string;
        }

    public function get() {
        if (!isset($buffer)) { $buffer = ""; }
        return $buffer;
        }

    public function write($string) {
        if (!isset($buffer)) { $buffer = ""; }
        $buffer = $buffer.chr(strlen($string)).$string;
        }

    public function read() {
        if (!isset($buffer)) { $buffer = ""; }
        $return = "";
        $str_len = substr($buffer,0,1); $buffer = substr($buffer,1,strlen($buffer)-1);
        $return = substr($buffer,0,$str_len); $buffer = substr($buffer,$str_len,strlen($buffer)-$str_len);

        return $return;
        }

    public function clear() {
        $buffer = "";
        }

    public function flushall() {
        echo $buffer;
        $this->clear();
        }

    public function close() {
        return new NoMethods();
        }
    }
?>

I don't get any errors when I create the new StringBuffer class, so I know that it is indeed including my files.

Answer 1

What's going on here is that inside your class methods, instead of accessing properties ( $this->buffer ) you are getting and setting local variables ( $buffer ) so the changes don't "stick".

That code could use some cleaning up too. There is lots of redundant stuff in there, for example:

public function set($string) {
    // isset will never return false, so this if will never execute
    // even if it did, what's the purpose of setting the buffer when you
    // are going to overwrite it one line of code later?
    if (!isset($this->buffer)) { $this->buffer = ""; }
    $this->buffer = $string;
}

Answer 2

I think that your class should be

class StringBuffer {
    private $buffer = "";

    public function get() {
        if (!isset($this->$buffer)) { $this->$buffer = ""; }
        return $this->$buffer;
        }

    public function write($string) {
        if (!isset($this->$buffer)) { $this->$buffer = ""; }
        $this->$buffer = $this->$buffer.chr(strlen($string)).$string;
        }
}

in this way you are setting a class variable, with your code you are just setting variables inside methods