MySQL connections and PHP - php

Question

I have a somewhat general question regarding what's best when programming in PHP using also database connections. I am building a project which includes several modules and each module needs to connect to the MySQL sometimes. The module files are included in the main index.php depending on the action selected from the menu by the user. I guess, most projects work this way anyway.
So far what I do is always open the connection at the start of each module file and close it after the queries have run.
My question is this: is it better to open the connection to the database in the beginning of the index.php and close it in the end so to have 1 connection open, or do multiple connections which stay open for less time? What's best for speed and overhead?

Answer 1

As N.B. pointed out, you should probably setup a class to handle all your database related tasks. I am posting a snippet from my code archives to illustrate how you can setup such a class. This is solely for purposes of illustrating and not guaranteed to work for you if you just copy and paste. It may need some refinement. It also makes use of the smarty class to process data views.
I recommend stripping out whatever you don't need. Set your MySQL connection params. In your index file, you can instantiate a SQL object and simply call the appropriate methods. The methods return and keep your result as both an associative and indexed array. Iterating through table rows is as easy as:
$SQL->GetRows('RowTemplate.tpl', 'StoredProcedure', 'Parameters');
FYI This is part of a bigger $Portal framework object in case you're wondering what the $Portal reference is to. $SQL merely extends $Portal.
I hope this helps. Good luck
class SQL {
/********** MEMBER VARIABLES **********************************************************************/
var $Connection; // DB connection handler
var $Result; // ResultSet returned from last call during life of object instance
var $RowCount; // RowCount for ResultSet returned from last call during life of object instance
var $ResultArray; // ResultSet Array returned from last call during life of object instance
var $Query; // Query last submitted during life of object instance
var $ErrorNumber; // Error number for error returned from last call during life of object instance
var $Error; // Error returned from last call during life of object instance
var $Message; // Messages returned during life of object instance
// Switches, flags, markers, etc
var $DebugMode;
var $LogActive;
var $ShowErrorMsg;
// Modules array
var $Modules;
// SQL Connection Info - PROTECTED!
protected $Host = "localhost";
protected $User = "mydatabase";
protected $Password = "mypassword";
protected $Schema = "myschema";
/********** MEMBER FUNCTIONS **********************************************************************/
// Object Constructor
function __construct() {
// Automatically open DB Connection
//$this->OpenDBConnection();
//echo "User Object Constructor<br>";
}
// Open new DB Connection
function OpenDBConnection() {
return ($this->Connection = mysqli_connect($this->Host, $this->User, $this->Password, $this->Schema))? true : false;
}
// Close DB Connection
function CloseDBConnection() {
mysqli_close($this->Connection);
//return true;
}
// Return error messages
function GetError() {
return $this->Error;
}
// Return last query string
function GetQuery() {
return $this->Query;
}
// Call, execute stored procedure and return result set
/* NOTES: The result set is always returned as an int array of associative arrays
That is, if $Result was returned, the first row would be referenced as $Result[0]
and any column of the first row would be referenced as $Result[0]['ColumnName']
COMMENTS: */
function CallProcedure($StoredProcedure) {
// Clear any System Errors
$this->ErrorNumber = '';
$this->Error = '';
// Open DB Connection
if(!$this->OpenDBConnection()) return false;
// Kill error if there are no extra Params passed
$Params = #func_get_arg(1);
// Build Query
$this->Query = "CALL $StoredProcedure ($Params)";
//if($this->Result = $this->Connection->query($this->Query)) {
if($this->Result = mysqli_query($this->Connection, $this->Query)) {
// Reset global Result Set
$this->ResultArray = Array();
// Set record count for current record set
$this->RowCount = 0;
while($Row = #mysqli_fetch_array($this->Result, MYSQLI_BOTH)) {
$this->ResultArray[$this->RowCount] = $Row;
$this->RowCount++;
}
// Close DB Connection
$this->CloseDBConnection();
return $this->ResultArray;
}
// Grab Error
$this->ErrorNumber = mysqli_errno($this->Connection);
$this->Error = mysqli_error($this->Connection);
// Close DB Connection
$this->CloseDBConnection();
return false;
}
/* Using Smarty class, return row template filled with record set from given stored procedure
EXAMPLE 1: Primary Function - Using data set from stored procedure
$Portal->SQL->GetRows('RowTemplate.tpl', 'StoredProcedure', 'Parameters');
EXAMPLE 2: Secondary Function - Using data set in second dimensional associative array
$Portal->SQL->GetRows('RowTemplate.tpl', 'ARRAY', $MyDataSetArray); */
function GetRows($RowTemplate, $Procedure) {
// Kill error if there are no extra Params passed
$Parameters = #func_get_arg(2);
// Set return string
$ReturnString = '';
// If Procedure is ARRAY then params are data set else Call procedure and return results array
$Result = ($Procedure=='ARRAY')? $Parameters : $this->CallProcedure($Procedure, $Parameters);
// Loop through result set initializing smarty obj for each row
$Count = 0;
while(IsSet($Result[$Count])) {
$RowTemplateObj = new Smarty;
$RowTemplateObj->assign('SCRIPT_NAME', SCRIPT_NAME);
$RowTemplateObj->assign('HOST_NAME', HOST_NAME);
// Loop though each result row as an associative array of column - values
foreach ($Result[$Count] as $Key => $Value) {
if(IsSet($Result[$Count][$Key])) $RowTemplateObj->assign($Key, (is_array($Value))?$Value:stripslashes($Value));
//if(IsSet($Result[$Count][$Key])) $RowTemplateObj->assign($Key, $Value);
}
$RowTemplateObj->assign('bgcolor', '{$bgcolor'. ($Count%2 + 1) .'}');
// Concatenate populated row into return string
$ReturnString .= $RowTemplateObj->fetch($RowTemplate);
$Count++;
}
return $ReturnString;
}
function GetSelectList($Procedure, $Parameters, $OptionValueField, $OptionNameField) {
// Kill error if there are no extra Params passed
$Selected = #func_get_arg(4);
// Set return string
$ReturnString = '';
// Get List Resultset
$Result = $this->CallProcedure($Procedure, $Parameters);
// Loop through result set and set <option> ta row
$Count = 0;
while(IsSet($Result[$Count])) {
$ReturnString .= '<option value="'.$Result[$Count][$OptionValueField].'"';
$ReturnString .= ($Selected==$Result[$Count][$OptionValueField])? ' selected ' : '';
$ReturnString .= '>'.$Result[$Count][$OptionNameField].'</option>';
$Count++;
}
return $ReturnString;
}
function Execute($SQL) {
// Clear any System Errors
$this->ErrorNumber = '';
$this->Error = '';
// Open DB Connection
if(!$this->OpenDBConnection()) return false;
// Assign Query
$this->Query = $SQL;
if($this->Result = mysqli_query($this->Connection, $this->Query)) {
// Reset global Result Set
$this->ResultArray = Array();
// Set record count for current record set
$this->RowCount = 0;
while($Row = #mysqli_fetch_array($this->Result, MYSQLI_BOTH)) {
$this->ResultArray[$this->RowCount] = $Row;
$this->RowCount++;
}
// Close DB Connection
$this->CloseDBConnection();
return $this->ResultArray;
}
// Grab Error
$this->ErrorNumber = mysqli_errno($this->Connection);
$this->Error = mysqli_error($this->Connection);
// Close DB Connection
$this->CloseDBConnection();
return false;
}

Answer 2

MAKE Saperate connections in same file and close them according.
/*****Connection for portal1 ******/
$portal1_link = mysql_connect('localhost','root','') or die('Cannot connect to the DB');
mysql_select_db('mylekha_auction',$portal1_link) or die('Cannot select the DB');
/*****Connection for portal2 ******/
$portal2_link = mysql_connect('localhost','root','') or die('Cannot connect to the DB');
mysql_select_db('mylekha_auction',$portal2_link) or die('Cannot select the DB');