添加选项卡以使用正则表达式锚定文本

Question

I have something like this ;

<a href="#" class="example">
Link 1
</a>
<a href="#" class="example">
Link 2
</a>
<a href="#" class="example">
Link 3
</a>

I want add tab before anchor text. Like this;

<a href="#" class="example">
  Link 1
</a>
<a href="#" class="example">
  Link 2
</a>
<a href="#" class="example">
  Link 3
</a>

How can I do this with regex?

</div>

Answer 1

Edit, following the question extension

From his comments, it now appears that the OP targets a more general use, adding \ts to indent all lines between the opening and closing tag.
Then its time to remember that regex is not a good way to parse HTML, as frequently observed here.

But in this yet not too wide context we can propose a solution.
Unless somebody finds a better solution, I don't see a way to do it without 2 nested steps:

$updated_text = preg_replace_callback(
    '/(<a[^>]*>)\s*(.*?)\s*(<\/a>)/s',
    function($matches) {
        return $matches[1]
          . "
" . preg_replace('/([^
]+)/', "\t$1", $matches[2])
          . "
" . $matches[3];
    },
    $text
);

Note that, in addition to be a poor way of doing it, it's much time consuming due to the .*? (not greedy) quantifier.

---

Initial answer

Thanks to the @bobblebubble suggestion I just understood what means "I want add tab" (I previously thought only to browser's tabs :).

But I find its solution a bit too general: it'll add tab to any line which is not a tag!
I'd prefer to closely look for only <a> tags, and only when presented like in the OP's example:

$updated_text = preg_replace('/(<a[^>]*>)\s*([^<]*)\s*<\/a>/', '$1
\t$2</a>', $text);

Here is it working: https://regex101.com/r/qo2N22/1.