PHP MYSQL PDO Database Connection - php

Question

I am using PHP to establish a connection to a MYSQL database using PDO. I keep getting this error:
Uncaught Error: Call to a member function query() on null
I am pretty new to this approach but why am I getting a null from the query?
This is the code calling the classes:
<?php
$data = new Data;
echo $data->connect();
$view = new View;
echo $view->getData();
?>
This is the query class with the problem I suspect:
<?php
class View extends Data {
public function getData() {
$sql = 'SELECT * FROM equipment';
$stm = $this->connect()->query($sql);
while ($row = $stm->fetch()) {
echo $row['manuName'] . '<br>';
}
}
}
?>
This is the connection class:
<?php
class Data {
private $dbHost = DB_HOST;
private $dbUser = DB_USER;
private $dbPass = DB_PASS;
private $dbName = DB_NAME;
private $dbHandler;
private $error;
public function connect() {
$con = 'mysql:host=' . $this->dbHost . ';dbname=' . $this->dbName;
$options = array(
PDO::ATTR_PERSISTENT => true,
PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION
);
try {
$this->dbHandler = new PDO($con, $this->dbUser, $this->dbPass, $options);
} catch (PDOException $e) {
$this->error = $e->getMessage();
echo $this->error;
}
}
}
I am not seeing my error. If anyone can see why I cannot pull the data.
Thank you

Answer 1

As u_mulder said in the comments,
your connect method will not return anything.
I updated it as below and made some change on your getData() method:
public function connect() {
$con = 'mysql:host=' . $this->dbHost . ';dbname=' . $this->dbName;
$options = array(
PDO::ATTR_PERSISTENT => true,
PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION
);
try {
//$this->dbHandler = new PDO($con, $this->dbUser, $this->dbPass, $options);
return new PDO("mysql:host=".$this->dbHost.";dbname=".$this->dbName,$this->dbUser,$this->dbPass);
} catch (PDOException $e) {
$this->error = $e->getMessage();
echo $this->error;
}
}
}
class View extends Data {
public function getData($table){
try {
$sql="SELECT * FROM $table";
$q = $this->connect()->query($sql) or die("failed!");
while($r = $q->fetch(PDO::FETCH_ASSOC)){ $data[]=$r; }
return $data;
}
catch(PDOException $e)
{
echo 'Query failed'.$e->getMessage();
}
}
}
$view = new View;
$result = $view->getData('equipment');
print_r($result);
Although I prefer remove connect method and add a constructor in your Data class as below:
public $this->conn;
public function __construct(){
$this->conn = new PDO("mysql:host=".$this->dbHost.";dbname=".$this->dbName,$this->dbUser,$this->dbPass);
}
and then change my getData as below:
$q = $this->conn->query($sql) or die("failed!");
‌Because as ADyson said in the comments :
you shouldn't really be connecting again every time you run a query..

Answer 2

Thanks again Ali, ADyson & u_mulder,
If I understand what all comments are saying, this code should factor in your advice. Can you please tell me if this is a better approach if you have the time.
Data Class:
<?php
class Data {
private $dbHost = DB_HOST;
private $dbUser = DB_USER;
private $dbPass = DB_PASS;
private $dbName = DB_NAME;
private $error;
public $this->conn;
public function __construct(){
$this->conn = new PDO("mysql:host=".$this->dbHost.";dbname=".$this->dbName,$this->dbUser,$this->dbPass);
}
try {
return new PDO("mysql:host=".$this->dbHost.";dbname=".$this->dbName,$this->dbUser,$this->dbPass);
} catch (PDOException $e) {
$this->error = $e->getMessage();
echo $this->error;
}
}
}
View Class:
<?php
class View extends Data {
public function getData($table){
try {
$sql="SELECT * FROM $table";
$q = $this->conn->query($sql) or die("failed!");
while($r = $q->fetch(PDO::FETCH_ASSOC)){ $data[]=$r; }
return $data;
}
catch(PDOException $e)
{
echo 'Query failed'.$e->getMessage();
}
}
}
Output:
<?php
$view = new View;
$result = $view->getData('equipment');
print_r($result);
?>
This code is still giving errors:
unexpected '->' (T_OBJECT_OPERATOR), expecting ',' or ';'