PHP Callback function not working on object functions - php

Question

I have an array and want to apply MySQLi->real_escape_string on every member of the array through array_walk but this is not working:
array_walk($array, '$mysqli->real_escape_string');
It gives this error:
Warning: array_walk() expects parameter 2 to be a valid callback, function '$mysqli->real_escape_string' not found or invalid function name in C:\wamp\www\ts.php on line 69
$mysqli is a valid object and works fine if I do $mysqli->real_escape_string('anything') on anything else.
My Question: Is it not possible to pass object's functions as callback ? Or am I doing something wrong.
IMPORTANT: I know I can create my own callback function and implement $mysqli->real_escape_string in it BUT I want to know is it not possible to use callback as an object's function ?

Answer 1

If your calling a method within an object you should pass in an array, first item being the object / context and then second should be the method:
Small example
function callback()
{
//blah
}
the above is called a function and should be called like so: array_walk($array, 'callback');
class object()
{
public function callback()
{
}
}
the above callback is called a method, its practically the same as a function but because its within a class it has a parent context, so should be called like so:
$object = new object();
array_walk($array, array($object , 'callback'));
MySQLi is an object orientated library so after you have initialized your mysqli object you should call the "method" like so:
array_walk($array, array($msqli, 'real_escape_string'));
Also as mentioned above, array_walk will walk both key and value into the mysql object witch will cause in exact escaping, you should use array_map to walk the values alone:
array_map($array, array($msqli, 'real_escape_string'));

Answer 2

As you can read on php callback page, you shall use:
# produces an error
array_walk($array, array($msqli, 'real_escape_string'));
array_map($array, array($msqli, 'real_escape_string'));

Answer 3

array_walk will only allow a user defined function to be passed as the callback, not a core PHP function or method. To do this I would try the following:
foreach($array as &$value) {
$value = $mysqli->real_escape_string($value);
}
Passing the value by reference allows it to be modified within the foreach loop, resulting in each member of the array being escaped.

Answer 4

I found this post to be quite useful when figuring out how to get array_walk() to work in methods within a class. Adding it to this thread in case it helps others out.