assigning a variable a function in php 5.3.15

Hi, my system goes down, when defining the following lambda function:

$stripDatabaseSlashes = function ($value) {
  return str_replace('`', '', $value);
};
return array_map($stripDatabaseSlashes, $this->columns);

What can it be - I have php 5.3.15 and assigning variables functions works when testing on the php console "php -a"..