Need help with classes.

[Shabalaka]

Hi guys

I have a general query regarding PHP Classes and the uses of them

I understand how the classes work and how to code them but am not too sure about how to use them effectively.

I tried to search on google for some advice and help of when to and when not to use classes in PHP , But they all seem to lead me to beginning tutorials.

Any help or pointers would be appreciated

Many Thanks Shab.

[laserlight]

There is a recent thread on OOP & OOP Books from which you might find something that you can read and apply.

[Shabalaka]

Thanks for the reply , I will look at some of those books 🙂

Just as an example here is a class i wrote while i am still trying to grasp the concept of when classes become more useful.

<?php
include_once("connectionDetails.php");
include_once('functions/_cleanData.php');



class Query{

	public $table;
	public $sql;
	public $queryID;

	public function multiInsertSQL($arrayValues,$arrayFields,$table){
		$this->table = cleanData($table);
		$openConnection = new connection();
		$openConnection->connectServer();


		$this->sql = "INSERT INTO `".$this->table."`  (";
		$this->appendSQL($arrayFields,"`");
		$this->sql .= ") VALUES (";
		$this->appendSQL($arrayValues,"'");
		$this->sql .= ");";

	}

	public function simpleSelect($table){



		$this->sql = "SELECT * FROM `".cleanData($table)."`";
		//echo $this->sql;


	}

	public function returnRows(){
		$array = array();
		while($row = mysql_fetch_array($this->queryID)){
			array_push($array,$row);

		}

		return $array;

	}



	public function runQuery(){

		$this->queryID = mysql_query($this->sql) or die ("SQL ERROR ".mysql_error());

	}

	public function success(){

		return true;
		//

	}

	public function numRowsFound(){


		return mysql_num_rows($this->queryID);


	}

	public function returnRow(){


		return mysql_fetch_array($this->queryID);

	}
	public function queryRow($value,$field,$table){

		$this->sql = "SELECT * FROM `".cleanData($table)."` WHERE ";
		//$this->appendSQL($value);	
		$valueAmount = returnArrayNum($value);
			for($i=0;$i<$valueAmount;$i++){
			//Clean each field

				$this->sql .= "`".cleanData($field[$i])."` =  '".cleanData($value[$i])."' AND ";

		}

		$this->sql = substr($this->sql, 0 , -4);
			//displayClass($this);





	}
	public function appendSQL($array,$breaker){


		$valueAmount = returnArrayNum($array);
		for($i=0;$i<$valueAmount;$i++){
			//Clean each field


				$this->sql .= $breaker.cleanData($array[$i]).$breaker.",";



		}
		$this->sql = substr($this->sql,0,-1);	
	}	
}
?>

The other functions look like this.

	function cleanData($string){
		$cleanString = mysql_real_escape_string($string);
		return $cleanString;
		//$newConnection->closeConnection();	
	}

function isNothing($string){

	if($string == ""){
		//String is nothing.
		return true;	

	}else{
		//String has a value;
		return false;
	}


}
function returnArrayNum($array){

	return count($array);


}

Is this an "effective" use of classes and functions though ?

Regards Shab

[Shabalaka]

As you can see what i tried to do is have a SQL generated from the values passed from a form.

Only downside i can see at the moment is that all fields must match a tables fields.

If theres anything else i have missed , Please tell me 🙂 Its all a learning curve at the moment

Regards Shab

[TheoGB]

PHP's not really a very good OOP language, in my experience but it has some good stuff going on.

When I designed my CMS I started, like you, by putting my DB functions into a class, but actually this proved more trouble that it was worth, since I had to instantiate the class at the start of any page where I was doing DB calls and then all calls had to be made in the form DBClass->method().

As such I created a single DB include file that had the necessary functionality.

However, I do create a class for each table on my database (excluding linking tables) and I instantiate those whenever I'm working on that table. For these I created a base abstract class that gives me all the CRUD functionality in a way that is easy to reuse.

Then you inherit and expand the abstract class whenever you create a class for a given database table.

In other cases, utility functions, etc. I tend to just use standalone functions in include files. Each class gets its own file too. In the classes folder I have a single 'include_all_classes.php' file and then I have an over all 'include_all.php' file that sets sessions up, and instantiates my Smarty class for output as well as including my include_all_classes.php and include_all_inc.php files.

[TheoGB]

Oh and you will of course have to always know your database column names and types so that's a given that you'll send that stuff through.

But if you're doing code you want to be as generic as possible you can use:

foreach($array as $key => $value)
{
}

very effectively to let you set the $keys elsewhere (to match your columns) and use the same method over and over.

You can also use argc and http://www.php.net/manual/en/reserved.variables.argv.php]argv[/url] to let you have functions that can take an open ended number of arguments, which is very useful for making a generic query handling function that uses mysql_real_escape_string() effectively.

[Shabalaka]

Thanks for the reply 🙂

Im intrigued by the using a class for each table idea , I would never have thought of that one. 😉

I think thats quite a neat way of doing things.

And as you said yes i need to instantiate each call of my DB class i have at the moment

Would it be possible to show an example of how you are using each class for a table please?

Just so i can get a rough idea of how you are using a table class

Yes as you see on my multiInsertSQL method i prebuild a SQL statement from 2 sets of arrays and values.

trying to save writing INSERT INTO table (field,field`) etc... all the time 🙂
Regards Shab.

[TheoGB]

The abstract class is something like this:

abstract class Control
{
	abstract protected function amendRecord();
	abstract protected function createRecord();
	abstract protected function deleteRecord($id);
	abstract protected function deleteSelected(array $id_array);
	abstract protected function loadForm($sub_op);

protected $date_fields;
protected $retrieve_order;
protected $form;		/* The data for HTML form to update/create the object */
public $table;			/* The full data from the table */
public $errors;			/* An array of strings detailing any issues. */
public $table_name;		/* This will hold the name of the table for SQL queries */
public $records;		/* Will hold the total number of records in the table */
public $paginate;		/* Paginate the records with a limit flag */
public $records_per_page;
public $current_page;


/** Constructor
 * Sets members up as arrays.
 * 
 * @return 
 */
public function __construct($order = 'id DESC', $paginate = 'no', $records_per_page = 10)
{
	$this->form = array();
	$this->table = array();
	$this->errors = array();
	$this->date_fields = array('entered', 'posted', 'taken', 'on_date');
	$this->time_fields = array('at_time');
	$this->retrieve_order = $order;
	$this->paginate = $paginate;
	$this->records_per_page = $records_per_page;
	$this->current_page = 0;
	$this->getPageLimits();
	$this->retrieveAll();
}


/** updateFromForm
 * This function reads through the form array member, which has
 * previously been filled by the parseForm method, and builds
 * an update query by examining types. It is therefore generic.
 * 
 * @return $result Array
 */
protected function updateFromForm()
{
	$query_string = 'UPDATE '.$this->table_name.' SET ';
	$values = array();

    foreach($this->form as $key => $value) 
	{
        if($key == 'id') 
		{
          $query_append = " WHERE id = %d";
          $values_append = $value;
        } 
		else if (in_array($key, $this->date_fields))
		{
			$value = convert_date($value, "YYYY-MM-DD");
			$query_string .= "`".$key."`=%s, ";
			array_push($values, $value);
		}
		else if (in_array($key, $this->time_fields))
		{
			$value = convert_time($value, "hh:mm:ss");
			$query_string .= "`".$key."`=%s, ";
			array_push($values, $value);
		}
		else if ($key == 'password')
		{
            /* Do nothing */				
		}
		else 
		{
          if (is_float($value))
            $query_string .= "`".$key."`=%f, ";
          else if (is_numeric($value))
            $query_string .= "`".$key."`=%d, ";
          else
            $query_string .= "`".$key."`=%s, ";

          array_push($values, $value);
        }
    }

    $query_string = rtrim($query_string, " ,");
  	$query_string .= $query_append;
    array_push($values, $values_append);

    return run_query($query_string, $values);
}


/** insertFromForm
 * This function reads through the form array member, which has
 * previously been filled by the parseForm method, and builds
 * an update query by examining types. It is therefore generic.
 * 
 * @return $result Array
 */
protected function insertFromForm()
{		
	$query_string = 'INSERT INTO '.$this->table_name.' VALUES(';
	$values = array();

    foreach($this->form as $key => $value) 
	{	 
        if($key == 'id')
		{ 
        	$query_string .= "NULL, ";
		}
		else if (in_array($key, $this->date_fields))
		{
			$value = convert_date($value, "YYYY-MM-DD");
			$query_string .= "%s, ";
			array_push($values, $value);
		}
		else if (in_array($key, $this->time_fields))
		{
			$value = convert_time($value, "hh:mm:ss");
			$query_string .= "%s, ";
			array_push($values, $value);
		}
		else if ($key == 'password')
		{
            $query_string .= "PASSWORD(%s), ";
			array_push($values, $value);
		}
        else 
		{
          if (is_float($value))
            $query_string .= "%f, ";
          else if (is_numeric($value))
            $query_string .= "%d, ";
          else
            $query_string .= "%s, ";

          array_push($values, $value);
        }
	}

    $query_string = rtrim($query_string, " ,");
	$query_string .= ")";		

    return run_query($query_string, $values);
}


/** deleteMultipleEntries
 * Cycles through an array of ids deleting them all.
 * 
 * @return 
 * @param $id_array Object
 */
protected function deleteMultipleEntries($id_array)
{
	if(count($id_array) == 0)
		return 0;

	for($i = 0; $i<count($id_array); $i++)
		run_query('DELETE FROM '.$this->table_name.' WHERE id = %d', $id_array[$i]);

	return count($id_array);
}


/** parseForm
 * The parseForm function will determine if we have submitted a form
 * and if so it will load the form data into the form member of the 
 * class. This data will be used by Smarty.
 * 
 * @return Nothing
 */	
public function parseForm()
{
	if ((isset($_POST['sub_op'])) && ($_POST['sub_op']))
		$sub_op = strtolower($_POST['sub_op']);
	else
		$sub_op = '';

/* Load form should clear the form if there is no $sub_op */
	if ($this->loadForm($sub_op))
	{
		switch ($sub_op)
		{
			case 'amend': $this->amendRecord();
				break;
			case 'create': $this->createRecord();
				break;
			case 'delete': $this->deleteRecord();
				break;
			case 'delete selected': $this->deleteSelected($_POST['del_array']);
				break;
			default: /* Do nothing as there has been no request made */
		}

	/* Clear the form */	
		$this->loadForm('');			
	}

	$this->retrieveAll();
}


/** formToScreen
 * Move the form fields to a Smarty Object for display on screen.
 * 
 * @return 
 * @param $SmartyObject Object
 */
public function formToScreen(&$SmartyObject) 
{
	foreach($this->form as $key => $value)
	{
		$SmartyObject->assign("$key", $value);
	}	
}


/** retrieveRecord
 * This function provides two duties:
 * 1. Sets up the form if an 'amend' hyperlink has been 
 * 		selected, retrieving the record to the form and
 * 		converting the date from DB form to screen.
 * 2. Maintain current versions of the form data in the 
 * 		case of an Amend update error.
 * 
 * @return Text for the form button.
 */
public function retrieveRecord() 
{
	if (isset($_GET['link_op']) && ($_GET['link_op'] == 'amend'))
	{
		$result = run_query('SELECT * FROM '.$this->table_name.' WHERE id = %d', $_GET['id']);

		if(!$result)
		{
			$err_string = ucfirst($this->table_name)." ".$id." not found.";
			array_push($this->errors, $err_string);	  	
		}
		else
		{
			foreach($result[0] as $key => $value)
			{
				if (in_array($key, $this->date_fields))
				{
					$value = convert_date($value, "DD/MM/YY");
				} 
				elseif (in_array($key, $this->time_fields))
				{
					$value = convert_time($value);
				}
				$this->form[$key] = $value;						
			}
			return 'Amend';
		}
	}

/* We allow for an error in the amend, e.g. blank fields that shouldn't be */
	if (isset($_POST['sub_op']) && (strtolower($_POST['sub_op']) == 'amend') && (count($this->errors)>0))
		return 'Amend';

	return '';
}


/** displayRecord
 * Puts a record into an array for display purposes
 * and returning it. This will parse every value for 
 * output with line breaks and fix the dates.
 * 
 * @return Array Object of the record
 */
public function displayRecord() 
{
	if (isset($_GET['link_op']) && ($_GET['link_op'] == 'display'))
	{
		$result = run_query('SELECT * FROM '.$this->table_name.' WHERE id = %d', $_GET['id']);
		if(!$result)
		{
			$err_string = ucfirst($this->table_name)." ".$id." not found.";
			array_push($this->errors, $err_string);
			return false;
		}
		else
		{
			$output = array();
			for($i=0; $i<count($result); $i++)
			{
				$output[$i] = parse_record($result[$i], $this->date_fields);
			}
			return $output;
		}			
	}		
	return '';
}



/** retrieveOrdered
 * Retrieve all records in an order
 * 
 * @return 
 */
public function retrieveOrdered($where_condition, $order_condition)
{
	$result = run_query('SELECT * FROM '.$this->table_name.' WHERE '
							.$where_condition.' ORDER BY '.$order_condition);
	if(!($result)) return 0;

	for ($i = 0; $i<count($result); $i++)
	{
		foreach($result[$i] as $key => $value)
		{
			if (in_array($key, $this->date_fields))
			{
				$value = convert_date($value, "dd month year");
				$result[$i][$key] = $value;
			}
			elseif (in_array($key, $this->time_fields))
			{
				$value = convert_time($value);
				$result[$i][$key] = $value;
			}
		}
	}
	return $result;
}	
} 

[TheoGB]

I had to chop out some functions to fit in with the maximum post length, I'm afraid. It's very old code. Hopefully it will give you some idea of how I'm running it.

My Run_query() function is more along the lines of printf() in style. So you get:

$result = run_query("INSERT INTO ."$this->table_name." VALUES(NULL, %d, %s, %s)". $integer_var, $string_var, $another_char_var);

And inside run_query we check the arguments:

  $args = func_get_args();
  array_shift($args);

Then I can cycle through $args, which is an array of the other arguments, and deal with each based on the query having %d or %s, doing html_real_escape_string() to the %s elements only.