Zend framework - PDO source code - php

Question

I have a little question just for educational purpose...
I was digging into Zend Framework's code, in order to learn how it works "from the inside", and I stopped at this little piece of code : (Their implementation of bindParam() from PDO) :
/**
* Binds a parameter to the specified variable name.
*
* #param mixed $parameter Name the parameter, either integer or string.
* #param mixed $variable Reference to PHP variable containing the value.
* #param mixed $type OPTIONAL Datatype of SQL parameter.
* #param mixed $length OPTIONAL Length of SQL parameter.
* #param mixed $options OPTIONAL Other options.
* #return bool
*/
public function bindParam($parameter, &$variable, $type = null, $length = null, $options = null)
{
if (!is_int($parameter) && !is_string($parameter)) {
/**
* #see Zend_Db_Statement_Exception
*/
require_once 'Zend/Db/Statement/Exception.php';
throw new Zend_Db_Statement_Exception('Invalid bind-variable position');
}
$position = null;
if (($intval = (int) $parameter) > 0 && $this->_adapter->supportsParameters('positional')) {
if ($intval >= 1 || $intval <= count($this->_sqlParam)) {
$position = $intval;
}
} else if ($this->_adapter->supportsParameters('named')) {
if ($parameter[0] != ':') {
$parameter = ':' . $parameter;
}
if (in_array($parameter, $this->_sqlParam) !== false) {
$position = $parameter;
}
}
if ($position === null) {
/**
* #see Zend_Db_Statement_Exception
*/
require_once 'Zend/Db/Statement/Exception.php';
throw new Zend_Db_Statement_Exception("Invalid bind-variable position '$parameter'");
}
// Finally we are assured that $position is valid
$this->_bindParam[$position] =& $variable;
return $this->_bindParam($position, $variable, $type, $length, $options);
}
The thing that I don't understand, is that at the end of the function, they return
return $this->_bindParam($position, $variable, $type, $length, $options)
which is declared as an array ...
/**
* Query parameter bindings; covers bindParam() and bindValue().
*
* #var array
*/
protected $_bindParam = array();
How can they return an array and pass parameters to it ?
Moreover, I can find any condition to stop the recursion...
You can find the link for the file here :
http://framework.zend.com/svn/framework/standard/trunk/library/Zend/Db/Statement.php

Answer 1

Zend_Db_Statement is an abstract class.
Unless I am mistaken, all classes that inherit from Zend_Db_Statement declare a _bindParam() method.
for example in Zend_Db_Statement_Pdo:
class Zend_Db_Statement_Pdo extends Zend_Db_Statement implements IteratorAggregate
{
...
protected function _bindParam($parameter, &$variable, $type = null, $length = null, $options = null)
{
...
}
}