如何捕获以＃标签开头的子串？

I'm looking for php code to split word from text using regex, preg_match() , preg_split(), or any other way.

$textstring="one #two three #four #five";

I need to get #two,#four, and #five saved as array elements.

Try splitting by this: \b #

preg_split("/\\b #/", $text)

Try this:

$text="one #two three #four #five";
$parts = array_filter(
    explode(' ', $text), // split into words
    function($word) {
        // filter out all that don't start with '#' by keeping all that do
        return strpos($word,"#")===0; 
        // returns true when the word starts with "#", false otherwise
    }  
);
print_r($parts);

You can see it here: https://3v4l.org/YBnu3

You may also want to read up on array_filter

Use a negated character class after the # symbol for highest pattern efficiency:

Pattern: (Demo)

#[^ ]+  #this will match the hashtag then one or more non-space characters.

Code: (Demo)

$in='one #two three #four #five';
var_export(preg_match_all('/#[^ ]+/',$in,$out)?$out[0]:'failed');  // access [0] of result

Output:

array (
  0 => '#two',
  1 => '#four',
  2 => '#five',
)