php-regexHow to use PHP regex to match a hashtag?

Using PHP regex to match a hashtag is a simple process. The following example code block will match a hashtag in a string:

$string = 'This is a #hashtag';
preg_match('/#([a-zA-Z0-9_]+)/', $string, $matches);

The output of the example code will be:

Array
(
    [0] => #hashtag
    [1] => hashtag
)

Code explanation

$string = 'This is a #hashtag';: This is the string that contains the hashtag.
preg_match('/#([a-zA-Z0-9_]+)/', $string, $matches);: This is the regular expression used to match the hashtag. The # symbol is used to match the hashtag, and the ([a-zA-Z0-9_]+) part is used to match the characters in the hashtag.
$matches: This is the array that will contain the matches from the regular expression.