How to find and replace code in markdown line?

Question

PHP

How to extract code from markdown text?
in the text, the code can occur several times,
right now I wrote the following algorithm:

• markdown text convert to html using this package
  
• find tags in html"<pre><code >"
  
• extract all text up to closing tags
  

this is the first part of the program, simpler, then more difficult:
you need to find and replace this piece of code in markdown with a special label, like this: {это метка 1}
I will give an example, there is text:

Lorem ipsum is placeholder text commonly used in the graphic, print, and publishing industries for previewing layouts and visual mockups.
```
var ipsum = "123";
var ipsum2 = '321';
```
Lorem ipsum is placeholder text.
```
var ipsum3 = "456";
var ipsum4 = '654';
```
Don't!

Now we need to get both pieces of code in a separate array and replace them in markdown with special labels.
I can give my code as an example, but it is quite large, and I think that the direction I have chosen is not correct. Project on Laravel.
It is better to find the code in Mardkdown right away than to use html for this purpose.

Answer 1

'/^```\w*\n(.*?)^```/ms'
preg_match_all is just a search, and replacement is preg_replace or preg_replace_callback.