# In php regular expression

# In php regular expressions recently, when studying the source code of discuz, I found that one of the regular expressions is roughly the preg_match ('# ^ [a-z] #', "");

At the beginning, I suddenly got lost. Is this a match first? So ^ doesn't it indicate what to start? This is not a conflict. so I went to the official website and checked the usage of preg_match. I found several examples:

If (preg_match ("/\ bweb \ B/I", "PHP is the web scripting language of choice. ") {echo" A match was found. ";} else {echo" A match was not found. ";}

The definition of pattern is wrapped in //. after testing, I found that # can be replaced by //. in this case, everything is understood, the more things we learn, the more things we don't actually know. the larger the things we know, the longer the unknown side around him.