&引用

foreach中引用

$arr = [
            0 => ['name' => '张三', 'age' => 22, 'sex' => '男'],
            1 => ['name' => '小红', 'age' => 20, 'sex' => '女']
        ];
//没引用，值不改变
foreach ($arr as $v) {
   $v['name'] = '李四';
}
print_r($arr);

//使用key对数组重新赋值
foreach ($arr as $key => $v) {
    if ($v['name'] == '张三') {
        $arr[$key]['name'] = '李四';
    }
}
print_r($arr);

//有引用，值改变
foreach ($arr as &$v) {
    if ($v['name'] == '张三') {
        $v['name'] = '李四';
    }
}
print_r($arr);