.. _must-be-a-callable,-null-given:

must be a callable, null given
------------------------------
 
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Description
___________
 
The ``PDOStatement::fetchAll()`` accepts a 2nd argument as a callback. That method processes the returning rows before they are returned by the method itself. By default, the method returns arrays, and doesn't need the callback. When the callback is provided, it must be a valid callback, and, as such, can't be ``null``.

This error is the same as Argument #%d ($name) must be of type %s, %s given, but is specific to the PDO extension, and the ``PDOStatement::fetchAll()``. The original problem is also the same.

Example
_______

.. code-block:: php

   <?php
   
   // Connection to the database
   $db = new Pdo();
   
   // Dummy valid SQL query
   $stmt = $db->query('SELECT * FROM table');
   
   try {
       var_dump($stmt->fetchAll(PDO::FETCH_FUNC, NULL));
   } catch (\Throwable $e) {
       echo $e::class, ': ', $e->getMessage(), \PHP_EOL;
   }
   
   ?>

Solutions
_________

+ Remove the second ``$callback`` argument in the call to the ``PDOStatement::fetchAll()`` method.
+ Use a valid second ``$callback`` argument in the call to the ``PDOStatement::fetchAll()`` method.

Related Error Messages
______________________

+ :ref:`argument-#%d-($%s)-must-be-of-type-%s,-%s-given`