How to create a complex routine?

Hello people. I've been a desktop programmer for several years. Now I'm migrating a great software that works in a public school, done by me, for web. I have this client / server software inside the school, it supplies one local bank and another on the web. This on the web I'm accessing with KODULAR. So I'm recreating the routines that are in a desktop language for PHP + CODEIGNITER. CRUD is already in the test phase. But I have many business rule routines and in the language I've been working on for 20 years I do it fast. In the image I have a routine to include students in class journals. After entering the class number in (1) the school year (2) and clicking on (3), I search the database:
example :
Select table
Set order to indexname
seek textbox1.value+textbox2.value
if found()
  scan    //loop
    code
  enscan
 code 
 code...
endif

 and the result (names of school subjects) I enter in the list box (4) (5) (6) (7) (8), I enable (9) (10) and include the names of the students in (11). After selecting the student names in (11) these names appear in (12). The end of the routine happens when the user clicks the button (8). Loops, Inserts, Searches ... 
Selects - SQL returns the data in temporary tables named cursor.This cursor is a temporary table where I can also display data, search etc.
I have the knowledge that desktop and web programming we have to think a little different ....
I will have to do searches always using the Select where .. returning, rows or arrays .... and go working on those returns?
Is there an example of a routine with a database using PHP + CODEIGNITER commands and functions?
Thank you.

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What you want is to read up on CodeIgniters Query Builder in the CodeIgniter User's Guide.

CodeIgniter User Guide - Database Reference

What did you Try? What did you Get? What did you Expect?

Joined CodeIgniter Community 2009.  ( Skype: insitfx )

What you want is to read up on CodeIgniters Query Builder in the CodeIgniter User's Guide.

CodeIgniter User Guide - Database Reference

Ok ! Thanks !