PHP中的一个”坑“，PHP"坑"
说一个极有可能在工作中遇到的问题——foreach的引用
<span>$arr</span> = <span>range</span>(1,3<span>);
</span><span>//</span><span>[1,2,3]</span>
<span>foreach</span>(<span>$arr</span> <span>as</span> &<span>$val</span><span>) {
}
</span><span>foreach</span>(<span>$arr</span> <span>as</span> <span>$val</span><span>) {
}
</span><span>print_r</span>(<span>$arr</span><span>);
</span>登录后复制
上面这段代码输出什么呢，神奇的竟然是下面这样，这个我在工作中遇到过一次，当时弄了半天没弄出个所以然，只是找到了解决办法，这个问题解决办法有两个：
<span>Array</span><span>
(
[</span>0] => 1<span>
[</span>1] => 2<span>
[</span>2] => 2<span>
)</span>登录后复制
下面这两种方式都可以解决上面这个问题：
<span>//</span><span>方法1</span>
<span>foreach</span> (<span>$arr</span> <span>as</span> &<span>$value</span><span>) {
}
</span><span>unset</span>(<span>$value</span><span>);
</span><span>foreach</span> (<span>$arr</span> <span>as</span> <span>$value</span><span>) {
}
</span><span>print_r</span>(<span>$arr</span><span>);
</span><span>//</span><span>[1,2,3]
//方法2</span>
<span>foreach</span> (<span>$arr</span> <span>as</span> &<span>$value</span><span>) {
}
</span><span>foreach</span> (<span>$arr</span> <span>as</span> <span>$val</span><span>) {
}
</span><span>print_r</span>(<span>$arr</span><span>);
</span><span>//</span><span>[1,2,3]
//方法3</span>
<span>foreach</span> (<span>$arr</span> <span>as</span> &<span>$value</span><span>) {
}
</span><span>foreach</span> (<span>$arr</span> <span>as</span> &<span>$value</span><span>) {
}
</span><span>print_r</span>(<span>$arr</span><span>);
</span><span>//</span><span>[1,2,3]</span>登录后复制
方法1在官方的手册中也可以看到http://php.net/manual/en/control-structures.foreach.php，文章中专门有个tips提示这一点![PHP中的一个”坑“，PHP＂坑＂_PHP教程]()
$var = 123;
$tmp = &$var;
$tmp = 200;
echo $var;
//200
看看下面这张盗来的图（哈哈，原文链接贴在下面），对上面这个更好的理解
![PHP中的一个”坑“，PHP＂坑＂_PHP教程]()
php
$arr1 = array("a" => 1, "b" => 2, "c" => 3);
$arr2 = array("x" => 4, "y" => 5, "z" => 6);
foreach ($arr1 as $key => &$val) {}
foreach ($arr2 as $key => $val) {}
var_dump($arr1);
var_dump($arr2);
?>
The output is:
array(3) { ["a"]=> int(1) ["b"]=> int(2) ["c"]=> &int(6) }
array(3) { ["x"]=> int(4) ["y"]=> int(5) ["z"]=> int(6) }
参考文章：
http://www.cnblogs.com/CraryPrimitiveMan/p/4030748.html#3085766
http://www.jb51.net/article/39299.htm
本文版权归作者iforever(luluyrt@163.com)所有，未经作者本人同意禁止任何形式的转载，转载文章之后必须在文章页面明显位置给出作者和原文连接，否则保留追究法律责任的权利。
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