$re = '/@([^\s:]+)/';
$str = '@galaxy5univ I like you
RT @BestOfGalaxies: Let\'s sit under the stars ...
@jonghyun__bot .........((thanks)
RT @yosizo: thanks.ddddd <https://yahoo.com>
RT @LDH_3_yui: #fam, ccccc https://msn.news.com';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php