PHP function on SQL selectee

Question

Is it possible to perform a specific PHP function on data that is being returned by a database query, at the very moment this query is still running?

Let's say we are in some class and we have the following pseudo SQL which should return a couple of rows:

$results = $this->db->query("SELECT PHP_function(column), column 2 FROM table")->fetchAll(PDO::FETCH_ASSOC);

PHP_function could be json_decode for example.

Or is this not possible and would it require an additional loop on the results in order to do such a thing?

• moonwave99: Why would you want to do that at query time, and not later on?
• Mark Baker: Why do you need it as the query is running? What's wrong with looping through the data afterwards?
• Michael Berkowski: If you need functionality the RDBMS doesn't already provide (it provides a lot), you may need a user defined function
• user2180613: It's an additional loop.
• Ivan Yonkov: for me seems more legit: return php_function($row['column']); or even not returning, but using it somewhere inside the function

Answer 1

A manual page for the very function you're using contains an example

• user2180613: Any suggestions as to how I can force the arguments of PDO::FETCH_FUNC to be associative? PDO::FETCH_ASSOC does not achieve this. This is of course because arguments can't really be associative, thus receiving a numerically indexed array from func_get_args is natural behaviour. I would instead rather have one argument passed to the function of FETCH_FUNC, which would be an indexed array of the columns returned from the database query.
• Your Common Sense: I wouldn't waste time with research but rather use fetch() in a while loop instead of fetchAll() and apply whatever complex logic in this loop.

Answer 2

No, this is not possible. SQL engine (mysql or any other) is a separate application. PHP can communicate with it, send queries and receive data. Depending on what you want to do in that custom function, you may be able to write a custom function in mysql to do the same thing.

Have a look at create function documentation for info on how to do that.

• user2180613: Before PDO I used to be able to perform any function in the while loop ($row = mysql_fetch_assoc($query)) after the query, so I hoped there was some way to access this loop. I guess it's in the PDO fetchAll method. Edit: hadn't seen the answer of YCS, but StackoverFlow is now warning me to not accept anything within the next six minutes..
• Aleks G: @user2180613 This is not the same as you're asking. You can still do the loop, but you cannot use php function in the select clause.
• user2180613: I know it is not possible to mix the functions of two languages. See my question's first sentence.
• Aleks G: @user2180613 You asked whether it's possible to execute a function on a query when it's still running - and the answer is "no". When you're retrieving the data in a loop, the query has completed, it's not running any more.

Answer 3

Where's the problem with this?

<?php
 foreach($results as $key=>$res){
 $results[$key]['column'] = PHP_function($res['column']);
 }

Beside that MySQL has some useful functions included already, so maybe that one you need is usable right in the query

Answer 4

As i know it's not possible to achieve php manipulation while query running , you need to take result and then loop aur use predefined function from