PHP modifying array elements by reference - php

Question

I have a large data-set that I'm checking the contents of; I do this validation while creating an internal array of the data; to avoid looping over the array again later, I would like the validation to change the contents of the array.
Now the problem is that I'm calling the validation routines through call_user_func and this seems to pose some problems with passing by reference. Or maybe I'm doing something else wrong.
Here's a stripped down example:
public function index( )
{
$arr = array(
array('a' => 'aap', 'n' => 'noot', 'm' => 'mies'),
array('a' => 'ding', 'b' => 'flof', 'c' => 'bips'),
array( 'd' => 'do', 'e' => 're', 'c' => 'mi')
);
$func = array( $this, '_user_func' );
$errors = 0;
$new_arr = array();
foreach ($arr as $key => &$value) {
$new_arr[$key] = &$value; // Simulate production-code manipulation
//if ( !$this->_do_callback($func, $new_arr[$key], $key) ) $errors++; // No exception but array not modified afterwards
if ( !call_user_func( $func, $new_arr[$key], $key ) ) $errors++; // Exception: Parameter 1 to TestRef::user_func() expected to be a reference, value given
}
unset($value);
var_dump($new_arr);
print_r('Errors: '.$errors);
}
private function _do_callback( $func, array &$row, $row_id )
{
if ( is_callable( $func ) )
{
return call_user_func( $func, $row, $row_id );
}
else
{
throw new Exception( "Error doing callback. Callback empty or not a callable function." );
}
}
private function _user_func( &$arr, $index = 0 )
{
// "Validation" routine
foreach ($arr as $key => &$value) {
if ($key == 'b') return FALSE; // Simulate validation error for error count
$arr[$key] = 'replaced';
}
unset($value);
//var_dump($arr); // Works!
return TRUE;
}

Answer 1

i think you're trying to redefine an existing php function which is array_walk.
And especially in your case, you'll need array_walk_recursive.
Here's a rewritten (simplified ?) version of your code.
public function index( )
{
$arr = array(
array('a' => 'aap', 'n' => 'noot', 'm' => 'mies'),
array('a' => 'ding', 'b' => 'flof', 'c' => 'bips'),
array( 'd' => 'do', 'e' => 're', 'c' => 'mi')
);
$func = array( $this, '_user_func' );
var_dump($arr); // BEFORE WALK
array_walk_recursive($arr, $func);
var_dump($arr); // AFTER WALK
}
/**
* Does something to a row from an array (notice the reference)
*/
private function _user_func( &$rowValue, $rowIndex )
{
$rowValue = 'replaced';
}
You can see this code in action here --> http://ideone.com/LcZKo

Answer 2

Either:
Try changing your foreach loop into this:
foreach ($arr as $key => &$value) {
$this->_do_callback($func, $value, $key); // No exception but array not modified afterwards
//call_user_func( $func, $value, $key ); // Exception: Parameter 1 to TestRef::user_func() expected to be a reference, value given
}
unset($value); // avoid memory leak
Or:
Wrap the variable in an array prior to invoking call_user_func.

Answer 3

Have you tried it like this:?
foreach ($arr as $key => &$value) {
$this->_do_callback($func, $value, $key); // No exception but array not modified afterwards
//call_user_func( $func, $value, $key ); // Exception: Parameter 1 to TestRef::user_func() expected to be a reference, value given
}