Regular expression for laravel username and #tags - regex

Question

how can I set up a Regular expression for #username and #example on post field form, just like Twitter , when a user uses #hashtag in there post I will like to automatically save it to tag table and when a user uses #john symbol I would like to automatically notify the user he /she has been mentioned , please what is the logic behind this I don't have idea on how to start
im getting this error
BadMethodCallException
Method App\Http\Livewire\createPost::tag does not exist.
public function createPost()
{
if (auth()->check()) {
$this->validate();
$posts = Post::create([
'user_id' => auth()->user()->id,
'school_id' => $this->school,
'body' => $this->body,
'is_anon' => $this->is_anon,
$url = \url(route('posts.show', $this->id)),
]);
preg_match_all('/(?<=#)(\w+)/mi', $this->body, $matchedTags, PREG_SET_ORDER, 0);
foreach($matchedTags as $matchedTag) {
if(!$tag = tag::where('name', $matchedTag[0])->first()) {
$tag = tag::create(['name' => $matchedTag[0]]);
}
$this->tags()->attach($tag->id);
}

Answer 1

assuming your input string is $str, you can use these:
preg_match_all('/(?<=#)(\w+)/mi', $str, $atSignMatches, PREG_SET_ORDER, 0);
preg_match_all('/(?<=#)(\w+)/mi', $str, $poundMatches, PREG_SET_ORDER, 0);
and then you can print the $atSignMatches and $poundMatches which are the resulting values.
More info on https://www.php.net/manual/en/function.preg-match-all.php
Update: Steps
These are the steps to extract users and make notifications.
Get Request payload.
Extract Tags (using #)
Create Tag records in table
Extract mentions (using #)
Create notification for mentioners
public function save(Request $request) {
{
$post = Post::create($request->all());
$content = $post->content;
preg_match_all('/(?<=#)(\w+)/mi', $content, $matchedTags, PREG_SET_ORDER, 0);
foreach($matchedTags as $matchedTag) {
if(!$tag = Tag::where('name', $matchedTag[0])->first()) {
$tag = Tag::create(['name' => $matchedTag[0]]);
}
$post->tags()->attach($tag->id);
}
preg_match_all('/(?<=#)(\w+)/mi', $content, $matchedMentions, PREG_SET_ORDER, 0);
foreach($matchedMentions as $matchedMention) {
if($user = User::where('username', $matchedMention[0])->first()) {
$user->notifications()->create([
'post_id' => $post->id,
'type' => "MENTION",
'seen' => false,
'time' => \Carbon\Carbon::now()
]);
}
}
}
Notes:
Make sure to change the tag and notification creation implementation matching your table structure.