title: Checking value in an array inside one SQL query with WHERE clause
body: <p>I want to know is this practically possible in sql(using php as server-side), where in you have an array of values(numbers), and you try to retrieve data based on values inside that array..</p>
  
  <p>I have a sql table:</p>
  
  <pre><code>posts(
      id int(11) primary key,
      posts varchar(140),
      user_id int(11) foreign key
  );
  </code></pre>
  
  <p>I write a query now to retrieve 'posts':</p>
  
  <pre><code>$query="SELECT * FROM posts WHERE user_id=(**Array of select user_id's**)";
  </code></pre>
  
  <p>Is there any sql in-built function to check values inside an array? or should I be using PHP for this?</p>
  
  <p>I am actually trying to implement the twitter model of showing posts of people whom we follow.</p>