How to write helper class for different select operation? - php

Question

Guys i want different "select" operation as per my needs, but i just need one helper function for all select operation , How do i get it??
This is my helper class Database.php
<?php
class Database
{
public $server = "localhost";
public $user = "root";
public $password = "";
public $database_name = "employee_application";
public $table_name = "";
public $database_connection = "";
public $class_name = "Database";
public $function_name = "";
//constructor
public function __construct(){
//establishes connection to database
$this->database_connection = new mysqli($this->server, $this->user, $this->password, $this->database_name);
if($this->database_connection->connect_error)
die ("Connection failed".$this->database_connection->connect_error);
}
//destructor
public function __destruct(){
//closes database connection
if(mysqli_close($this->database_connection))
{
$this->database_connection = null;
}
else
echo "couldn't close";
}
public function run_query($sql_query)
{
$this->function_name = "run_query";
try{
if($this->database_connection){
$output = $this->database_connection->query($sql_query);
if($output){
$result["status"] = 1;
$result["array"] = $output;
}
else{
$result["status"] = 0;
$result["message"] = "Syntax error in query";
}
}
else{
throw new Exception ("Database connection error");
}
}
catch (Exception $error){
$result["status"] = 0;
$result["message"] = $error->getMessage();
$this->error_table($this->class_name, $this->function_name, "connection error", date('Y-m-d H:i:s'));
}
return $result;
}
public function get_table($start_from, $per_page){
$this->function_name = "get_table";
$sql_query = "select * from $this->table_name LIMIT $start_from, $per_page";
return $this->run_query($sql_query);
}
}
?>
In the above code get_table function performs basic select operation....
Now i want get_table function to perform all this below operations,
$sql_query = "select e.id, e.employee_name, e.salary, dept.department_name, desi.designation_name, e.department, e.designation
from employees e
LEFT OUTER JOIN designations desi ON e.designation = desi.id
LEFT OUTER JOIN departments dept ON e.department = dept.id
ORDER BY e.employee_name
LIMIT $start_from, $per_page";
$sql_query = "select id, designation_name from designations ORDER BY designation_name";
$sql_query = "select * from departments";
$sql_query = "select * from departments Limit 15,10";
So how to overcome this issue, can anyone help me out?

Answer 1

If you expand your class a bit, you could achieve what you are looking for. Something like this:
<?php
class Database
{
public $sql;
public $bind;
public $statement;
public $table_name;
protected $orderby;
protected $set_limit;
protected $function_name;
protected $sql_where;
protected $i;
protected function reset_class()
{
// reset variables
$this->sql = array();
$this->function_name = false;
$this->table_name = false;
$this->statement = false;
$this->sql_where = false;
$this->bind = array();
$this->orderby = false;
$this->set_limit = false;
}
protected function run_query($statement)
{
echo (isset($statement) && !empty($statement))? $statement:"";
}
public function get_table($start_from = false, $per_page = false)
{
// Compile the sql into a statement
$this->execute();
// Set the function if not already set
$this->function_name = (!isset($this->function_name) || isset($this->function_name) && $this->function_name == false)? "get_table":$this->function_name;
// Set the statement
$this->statement = (!isset($this->statement) || isset($this->statement) && $this->statement == false)? "select * from ".$this->table_name:$this->statement;
// Add on limiting
if($start_from != false && $per_page != false) {
if(is_numeric($start_from) && is_numeric($per_page))
$this->statement .= " LIMIT $start_from, $per_page";
}
// Run your query
$this->run_query($this->statement);
// Reset the variables
$this->reset_class();
return $this;
}
public function select($value = false)
{
$this->sql[] = "select";
$this->function_name = "get_table";
if($value != false) {
$this->sql[] = (!is_array($value))? $value:implode(",",$value);
}
else
$this->sql[] = "*";
return $this;
}
public function from($value = false)
{
$this->sql[] = "from";
$this->sql[] = "$value";
return $this;
}
public function where($values = array(), $not = false, $group = false,$operand = 'and')
{
if(empty($values))
return $this;
$this->sql_where = array();
if(isset($this->sql) && !in_array('where',$this->sql))
$this->sql[] = 'where';
$equals = ($not == false || $not == 0)? "=":"!=";
if(is_array($values) && !empty($values)) {
if(!isset($this->i))
$this->i = 0;
foreach($values as $key => $value) {
$key = trim($key,":");
if(isset($this->bind[":".$key])) {
$auto = str_replace(".","_",$key).$this->i;
// $preop = $operand." ";
}
else {
// $preop = "";
$auto = str_replace(".","_",$key);
}
$this->bind[":".$auto] = $value;
$this->sql_where[] = $key." $equals ".":".$auto;
$this->i++;
}
if($group == false || $group == 0)
$this->sql[] = implode(" $operand ",$this->sql_where);
else
$this->sql[] = "(".implode(" $operand ",$this->sql_where).")";
}
else {
$this->sql[] = $values;
}
if(is_array($this->bind))
asort($this->bind);
return $this;
}
public function limit($value = false,$offset = false)
{
$this->set_limit = "";
if(is_numeric($value)) {
$this->set_limit = $value;
if(is_numeric($offset))
$this->set_limit = $offset.", ".$this->set_limit;
}
return $this;
}
public function order_by($column = array())
{
if(is_array($column) && !empty($column)) {
foreach($column as $colname => $orderby) {
$array[] = $colname." ".str_replace(array("'",'"',"+",";"),"",$orderby);
}
}
else
$array[] = $column;
$this->orderby = implode(", ",$array);
return $this;
}
public function execute()
{
$limit = (isset($this->set_limit) && !empty($this->set_limit))? " LIMIT ".$this->set_limit:"";
$order = (isset($this->orderby) && !empty($this->orderby))? " ORDER BY ".$this->orderby:"";
$this->statement = (is_array($this->sql))? implode(" ", $this->sql).$order.$limit:"";
return $this;
}
public function use_table($table_name = 'employees')
{
$this->table_name = $table_name;
return $this;
}
}
To use:
// Create instance
$query = new Database();
// Big query
$query ->select(array("e.id", "e.employee_name", "e.salary", "dept.department_name", "desi.designation_name", "e.department", "e.designation"))
->from("employees e LEFT OUTER JOIN designations desi ON e.designation = desi.id LEFT OUTER JOIN departments dept ON e.department = dept.id")
->order_by(array("e.employee_name"=>""))
->limit(1,5)->get_table();
// More advanced select
$query ->select(array("id", "designation_name"))
->from("designations")
->order_by(array("designation_name"=>""))
->get_table();
// Simple select
$query ->use_table("departments")
->get_table();
// Simple select with limits
$query ->use_table("departments")
->get_table(10,15);
?>
Gives you:
// Big query
select e.id,e.employee_name,e.salary,dept.department_name,desi.designation_name,e.department,e.designation from employees e LEFT OUTER JOIN designations desi ON e.designation = desi.id LEFT OUTER JOIN departments dept ON e.department = dept.id ORDER BY e.employee_name LIMIT 5, 1
// More advanced select
select id,designation_name from designations ORDER BY designation_name
// Simple select
select * from departments
// Simple select with limits
select * from departments LIMIT 10, 15