variable assignment spanning multiple lines

Hello,

Indenting is missed on multi-line variable assignment, eg. for something like this I would expect the second and third line to indent:

```
$sql = "select something "
. "from somewhere "
. "where conditions=match";
```

Is there a way to configure that to happen?

Thanks...

查看 PHP 的 Vim 缩进脚本，可能在仓库的主缩进文件中。问题与使用点运算符进行多行字符串拼接有关。使用提供的示例测试当前行为，然后检查行连续的缩进规则。检查是否有配置选项，或者是否需要添加一条规则。通过编辑脚本并在 Vim 中测试来验证。

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