title: string arguments are not recognized by SWIG
body: <p>I have a frustrating problem which got me spend a lot of time dealing with it but I did not find any solution.</p>
  
  <p>I want to use C++ class in PHP with SWIG. I generated my shared object and it works fine for some methods but I've got this error whenever I call the methods with string arguments as their input:</p>
  
  <blockquote>
    <p>Fatal error: Type error in argument 2 of <code>PKI_Buf_initHex</code>. Expected <code>SWIGTYPE_p_std__string</code></p>
  </blockquote>
  
  <p><code>PKI_Buf_initHex</code> is the name of the wrapper class which SWIG made automatically. In my C++ code I declare <code>initHex</code> method as:</p>
  
  <pre><code>int initHex(const string x) 
  {..}
  </code></pre>
  
  <p>I included <code>typemaps.i</code> and <code>std_string.i</code> in my interface file but I got the same error message.</p>
  
  <p>I truly would appreciate if anyone can help me with this issue.</p>