Problem with definition/examples and theorem numbering

Question

I have a problem with my theorem and examples/definitions numbering. For my theorem environment I used the mdframed packages but for my definitions/examples I used \newtheorem{}{}. Here you can see that my theorem is numbered 3.5.1 but also my example is numbered as 3.5.1! How can I get a numeration like Theorem 3.5.1 and Example 3.5.2 and so on? Here there is my code:

\usepackage[framemethod=TikZ]{mdframed}

\newcounter{theo}[section]
\setcounter{theo}{0}
\renewcommand{\thetheo}{\arabic{chapter}.\arabic{section}.\arabic{theo}}

\theoremstyle{definition}
\newtheorem{definizione}{Definizione}[section]
\newtheorem{esempio}[definizione]{Esempio}
\newtheorem{algoritmo}[definizione]{Algoritmo}
\newtheorem{osservazione}[definizione]{Osservazione}
\theoremstyle{plain}
\newtheorem{corollario}[definizione]{Corollario}
\newtheorem{proposizione}[definizione]{Proposizione}


\newenvironment{theo}[2][]{%
   \refstepcounter{theo}%
   \ifstrempty{#1}%
      {\mdfsetup{%
         frametitle={%
            \tikz[baseline=(current bounding box.east),outer sep=0pt]
            \node[anchor=east,rectangle,fill=black!20]
            {\strut Teorema~\thetheo};}%
         }%
      }%
      {\mdfsetup{%
         frametitle={%            
            \tikz[baseline=(current bounding box.east),outer sep=0pt]
            \node[anchor=east,rectangle,fill=black!20]
            {\strut Teorema~\thetheo~(#1).};}%
         }%
      }%
   \mdfsetup{innertopmargin=10pt,linecolor=black!30,%
             linewidth=2pt,topline=true,%
             frametitleaboveskip=\dimexpr-\ht\strutbox\relax}
   \begin{mdframed}[backgroundcolor=gray!10]\relax\label{#2}}{\end{mdframed}%
}

Answer 1

You want that the environments share the theo counter:

\theoremstyle{definition}
\newtheorem{definizione}[theo]{Definizione}
\newtheorem{esempio}[theo]{Esempio}
\newtheorem{algoritmo}[theo]{Algoritmo}
\newtheorem{osservazione}[theo]{Osservazione}
\theoremstyle{plain}
\newtheorem{corollario}[theo]{Corollario}
\newtheorem{proposizione}[theo]{Proposizione}

Full code

\documentclass{book}
\usepackage{amsthm}

\usepackage[framemethod=TikZ]{mdframed}

\newcounter{theo}[section]
\setcounter{theo}{0}
\renewcommand{\thetheo}{\arabic{chapter}.\arabic{section}.\arabic{theo}}

\theoremstyle{definition}
\newtheorem{definizione}[theo]{Definizione}
\newtheorem{esempio}[theo]{Esempio}
\newtheorem{algoritmo}[theo]{Algoritmo}
\newtheorem{osservazione}[theo]{Osservazione}
\theoremstyle{plain}
\newtheorem{corollario}[theo]{Corollario}
\newtheorem{proposizione}[theo]{Proposizione}


\newenvironment{theo}[2][]{%
   \refstepcounter{theo}%
   \ifstrempty{#1}%
      {\mdfsetup{%
         frametitle={%
            \tikz[baseline=(current bounding box.east),outer sep=0pt]
            \node[anchor=east,rectangle,fill=black!20]
            {\strut Teorema~\thetheo};}%
         }%
      }%
      {\mdfsetup{%
         frametitle={%            
            \tikz[baseline=(current bounding box.east),outer sep=0pt]
            \node[anchor=east,rectangle,fill=black!20]
            {\strut Teorema~\thetheo~(#1).};}%
         }%
      }%
   \mdfsetup{innertopmargin=10pt,linecolor=black!30,%
             linewidth=2pt,topline=true,%
             frametitleaboveskip=\dimexpr-\ht\strutbox\relax}
   \begin{mdframed}[backgroundcolor=gray!10]\relax\label{#2}}{\end{mdframed}%
}


\begin{document}

\chapter{A}
\section{A}

\begin{theo}[Abc]{label}
Something
\end{theo}

\begin{esempio}
Example
\end{esempio}

\end{document}