Real example of "=&" usage

This question already has an answer here:

What do the “=&” and “&=” operators in PHP mean? 2 answers

---

Here's a very simple example. You are assigning the reference of $var1 to $var2 , so when you change $var2 , $var1 value changes.

<?php
$var1 = 10;
$var2 = 20;
$var2 = &$var1;
$var2 = 200;
echo $var1; // 200;

---

Suppose some user defined function manipulate a string:

function test($string){
    $string.='bar';
    return $string;
}

In this case, you would have to attribute the return of the function back to the variable:

$foo='foo';
$foo=test($foo);

Passing the variable by reference you could eliminate some code:

function test(&$string){
    $string.='bar';
}

$foo='foo';
test($foo);

Just like, for example, the native settype works. Look the ampersand at the manual.

---

Really useful example is modifying tree-alike structures:

Assuming you have a tree path like 'abc' and an array:

array(
    'a' => array(
        'b' => array(
            'c' => array(),
        ),
    ),
)

and you need to insert a new value in the deepest element. That you could end up with something like (not tested, just for demonstration purposes):

$parts = explode('.', $path);
$node = &$tree;
foreach ($parts as $part) {
    if (isset($node[$part])) {
        $node = &$node[$part];
    } else {
        $node = null;
        break;
    }
}

if (!is_null($node)) {
    $node[] = 'new value';
}

链接地址: http://www.djcxy.com/p/57590.html

上一篇: ＆（＆符号）符号在这种情况下意味着什么？

下一篇: “=＆”用法的真实例子