PHP通過引用傳遞參數

<?php
function add_some_extra(&$string) // 引入變量，使用同一個存儲地址
{
    $string .= 'and something extra.';
}
$str = 'This is a string, ';
add_some_extra($str);
echo $str;    // outputs 'This is a string, and something extra.'
?> 

輸出:
This is a string, and something extra.

如果沒有這個&符號，

<?php
function add_some_extra($string) 
{
    $string .= 'and something extra.';
}
$str = 'This is a string, ';
add_some_extra($str);
echo $str;    // outputs 'This is a string, '
?> 

輸出：
This is a string,