A weakly dynamically typed programming language (like PHP) made that the programmer's mistakes occur as non-coherent behaviours (for instance, the program gonna display stupid informations).
With a strongly dynamically typed language (like python), the programming mistakes causes error message. It makes the mistakes easier to uncover and diagnosis but in general the program became not usable after the message has been shown.
Finally, with a strongly statically typed language (like Java, Ada, OCaml, Haskell, ...) some mistakes can be uncovered at compile time and hence reduce the risk to provide an bugged program. (but the release occurs later)