title: PHP mysql auto increment passing BLANK into database
body: <p>Hi when I tried to pass a blank value for a primary key in a table, it gave me an error and it won't create/ update.
  For example, say id is primary key with auto increment
  INSERT INTO client (id, fname, lname) VALUES ('', 'bob', 'smith') won't work.</p>
  
  <p>How do I allow a blank value to pass for a primary key with auto increment?</p>
  
  <p>below is a part of my code:</p>
  
  <pre><code>protected static $table_name="client";
  protected static $db_fields=array('id', 'fname', 'lname');
  public $id;
  public $fname;
  public $lname;
  ...more code
  
  public function create() {
  
      global $database;
      $attributes = $this-&gt;sanitized_attributes();
      $sql = "INSERT INTO ".self::$table_name." (";
      $sql .= join(", ", array_keys($attributes));
      $sql .= ") VALUES ('";
      $sql .= join("', '", array_values($attributes));
      $sql .= "')"; 
      ...more code
  
  }
  </code></pre>
  
  <p>there is a lot more code but I cannot post them all here.
  I've tried array_shift() to get rid of the first key which is id but it gave me an error. this whole code is in a class called Client</p>