无法理解preg_match_all（）[重复]

Question

This question already has an answer here:

• Reference - What does this regex mean? 1 answer
• PHP preg_match and preg_match_all functions 4 answers

This question already has a duplicate question (Duplicate question)
I'm not able to create a comment there, so i'm creating a new one.

The solution provided is very explanatory, but I am still not able to get a clear view of preg_match_all() .

I tried the following code

preg_match_all("/#+([a-zA-Z0-9_]+)/i","#test this is #php test",$matches);

var_dump($matches)

The result is

array(2) {
  [0]=>
  array(2) {
    [0]=>
    string(5) "#test"
    [1]=>
    string(4) "#php"
  }
  [1]=>
  array(2) {
    [0]=>
    string(4) "test"
    [1]=>
    string(3) "php"
  }
}

My understanding is that the regex will only select the string starting with '#' as per my code.

But in the result, the array contains the string with '#' and without '#'.

Please help me figure this out. What am I missing.

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