title: Solve this PHP database error for me
body: <pre>
  Cannot add or update a child row: a foreign key constraint fails (`iwant2`.`product_tb`, CONSTRAINT `fk_clientID` FOREIGN KEY (`clientID`) REFERENCES `client_tb` (`clientID`))
  </pre>
  
  <p>Why am I getting this error?</p>
  
  <p>I have the following tables:</p>
  
  <ul>
  <li><code>client_tb</code></li>
  <li><code>product_tb</code></li>
  <li><code>category_tb</code></li>
  </ul>
  
  <p>I have the <code>productID</code>, <code>clientID</code> and <code>categoryID</code> in <code>product_tb</code>. The <code>clientID</code> and <code>categoryID</code> are in foreign relationship with <code>product_tb</code> table.</p>