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Today i have to solve a problem in MySql , The problem is i have two table in openCart 1. category_description category_id language name 1 1 category 1 2 1 category 2 3 1 category 3 4 1 category 4 5 1 category 5 6 1 category 6 7 1 category 7 8 1 category 8 1. product_category produc_id category_id 1 1 1 2 1 5 2 1 2 3 2 4 3 2 3 6 The resulting data should be like that produc_id category_name 1 category 1,category 2,category 5 2 category 1,category 3,category 4 3 category 2,category 6 I can do tha by in php by taking the category name to it's respective product id and implode them , but it will take much time and processor power cos the i have to do query every product id separately, I was searching the right query in MySql and found the function   GROUP_CONCAT()  http://dev.mysql.com/doc/refman/5.0/en/group-by-functions.html#function

Few days earlier I need to Create a text Or SCV file what will return some of the datafeed. Condition is i can't save the file in the serve i have to create and make to download for the user. So i made the below function   function genarateFeedTextFile($data=array(),$file_name=''){ $text=''; $temp=array(); if($data){ foreach($data as $value){          $text .= implode("\t",$value)."\n"; } } header("Content-Type: text/plain"); header("Content-disposition: attachment; filename=".$file_name.".txt");  header("Content-Transfer-Encoding: binary");  header("Pragma: no-cache");  header("Expires: 0"); echo $text; } This function solved my problem. But soon i have a little more problem. Some of my data contain new line "\n" or "\r" to tab "\b" so the result was not expected so i made a new function and puss all the string

To make  a Model   class Model<foldername><filename with out extention> extends Model{       public function methode(){     .....     }  }  We can call a model from controller using  $this->load->model('<folder>/<filename with out extention>'); And after that we can call the method like below $this->model_<folder>_<filename with out extention>->methode(); The Method should be public

(problem php session, session path , session.save_path) Few days ago i shifted few of my site to new server,  Soon we found that the user cannot login to the site. After searching the problem i found that the temporary directory that save the session file is not writable . To fine if the current session  is writable or not  : Below code will return you the current session path - ini_get("session.save_path"); Below code will return true or false, if the directory is writable the true else false- is_writable(ini_get("session.save_path")) if the current session save path is not writable the make it writable if that is not possible the change the path like ini_set("session.save_path","/tmp"); This code should place before session_start(); Or you can change the path in php.ini file the value of session.save_path  PHP : Session write problem