PHP 变量是按值传递还是按引用传递? [英] Are PHP Variables passed by value or by reference?

问题描述

PHP 变量是按值传递还是按引用传递?

Are PHP variables passed by value or by reference?

推荐答案

It's by value 根据 PHP 文档.

It's by value according to the PHP Documentation.

默认情况下，函数参数是按值传递的(这样，如果函数内参数的值发生更改，则不会在函数外更改).要允许函数修改其参数，它们必须通过引用传递.

By default, function arguments are passed by value (so that if the value of the argument within the function is changed, it does not get changed outside of the function). To allow a function to modify its arguments, they must be passed by reference.

要让函数的参数始终通过引用传递，请在函数定义中的参数名称前添加一个与号 (&).

To have an argument to a function always passed by reference, prepend an ampersand (&) to the argument name in the function definition.

<?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, and something extra.'
?>

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