$re = '/(\[(?:[^[\]]*?)\]\s*?(?=\[))|(\[(?:[^[\]]*?)\](?!\s*[\|&]\s*.))|(?:\[[^[\]]*?])|([^&\|\s]+)\s+(?=[^&\|\s]+)/';
$str = '[uname!uname] [uname!uname] | [submission_name !CustomValue] | [uname!uname] [submission_name!CustomValue] [uname> colin] 7 3&dsa | asf as d | [143 & t] | d d d';
preg_match_all($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