sha1 ( string
$str [, bool $raw_output = FALSE ] ) : stringSHA-1 belong to set of cryptographic hash functions SHA-1 designed by the United States National Security Agency (NSA). It's not recommended to use it for password storage like in case of MD5. SHA-1 was officially deprecated in 2011 and there are also collisions found. In 2017 Google have announced on their security blog, first SHA-1 collision:
https://security.googleblog.com/2017/02/announcing-first-sha1-collision.html