error in calling same function twice in php - php

Question

I have a function named record_list() which helps me echo fetched query from database every time I refresh/visit a page. I tried to use this function by echoing it twice but unfortunately all my DOM elements after the script get hidden and I can't use the following divisions/lists in my HTML. But if I call it once it's working fine without any problem.
Apart form this I am getting this error:
Fatal error: Call to a member function query() on a non-object
record_list():
function record_list(){
//include db configuration file
include_once("configuration.php");
try{
//MySQL query
$user_id = $_SESSION['user_id'];
$results = $mysqli->query("SELECT * FROM education_record WHERE user_id='$user_id' ");
//get all records from add_delete_record table
while($row = $results->fetch_assoc())
{
echo '<li class = "col-md-4 col-xs-12 records_display" id="item_'.$row["id"].'">';
echo '<div class="del_wrapper"><a href="#" class="del_btn" id="del-'.$row["id"].'">';
echo '<img src="../img/removeButtonIcon.svg" height ="20px" width ="20px" border="0" />';
echo '</a></div>';
echo '<div class="controls group_row">';
echo '<div class="controls group">';
echo '<input disabled type="text"class="group"style="width:175px" value ="'.$row["degree_name"].'"/>';
echo '<input disabled type="text"class="group"style="width:175px" value ="'.$row["institute"].'"/>';
echo '<input disabled type="text"class="group"style="width:175px" value ="'.$row["specialisation"].'"/>';
echo '<input disabled type="text"class="group"style="width:100px" value ="'.$row["date_of_passing"].'"/>';
echo '</div>';
echo '</div>';
echo '</li>';
}
}
catch (mysqli_sql_exception $e) {
throw $e;
die();
}
$mysqli->close();
//close db connection
}
configuration.php:
<?php
$host = 'localhost';
$dbname = 'databasename';
$username = 'username';
$password = 'can-be-anything';
try {
$mysqli = new mysqli($host, $username, $password, $dbname);
} catch (mysqli_sql_exception $e) {
throw $e;
die();
}
?>
Please help me identifying this error.

Answer 1

This is because you have to use include("configuration.php"); not include_once("configuration.php"); If you include_once, it will only work when the first instance of this configuration file is included in the script somewhere.
I would suggest making a class to wrap your connection saving it to a singleton state for use everywhere else in your script. Here is a simple example:
classes/class.DatabaseConfig.php
<?php
class DatabaseConfig
{
private static $singleton;
public function __construct()
{
if(empty(self::$singleton))
self::$singleton = $this;
return self::$singleton;
}
public function connect($host = "localhost", $username = "username", $password = "password", $database = "database")
{
// Create connection
try {
$mysqli = new mysqli($host, $username, $password, $database);
return $mysqli;
} catch (mysqli_sql_exception $e) {
throw $e;
die();
}
}
}
classes/class.Db.php
<?php
class Db
{
private static $singleton;
public static function mysqli()
{
if(empty(self::$singleton)) {
$con = new DatabaseConfig();
self::$singleton = $con->connect();
}
return self::$singleton;
}
}
index.php
<?php
// Look into using spl_autoload_register() here
include_once("classes/class.DatabaseConfig.php");
include_once("classes/class.Db.php");
// This will work
$con = Db::mysqli();
function myQuery()
{
// This will also work, so long as you have included the class
// file once before this function (not necessarily in this function either)
// is called to use
$con = Db::mysqli();
}

Answer 2

This happens because you close connection with $mysqli->close(); every time function is executed but, as #Rasclatt suggested, you open connection only once with include_once directive. You may replace include_once with include or try #Rasclatt OOP approach but if you don't want to dive into OOP for some reason I suggest to separate connection operation from the function and pass it to the function as a parameter like this
include_once("configuration.php");
function record_list($mysqli){
try{
//MySQL query
$user_id = $_SESSION['user_id'];
$results = $mysqli->query("SELECT * FROM education_record WHERE user_id='$user_id' ");
//get all records from add_delete_record table
while($row = $results->fetch_assoc())
{
echo '<li class = "col-md-4 col-xs-12 records_display" id="item_'.$row["id"].'">';
echo '<div class="del_wrapper"><a href="#" class="del_btn" id="del-'.$row["id"].'">';
echo '<img src="../img/removeButtonIcon.svg" height ="20px" width ="20px" border="0" />';
echo '</a></div>';
echo '<div class="controls group_row">';
echo '<div class="controls group">';
echo '<input disabled type="text"class="group"style="width:175px" value ="'.$row["degree_name"].'"/>';
echo '<input disabled type="text"class="group"style="width:175px" value ="'.$row["institute"].'"/>';
echo '<input disabled type="text"class="group"style="width:175px" value ="'.$row["specialisation"].'"/>';
echo '<input disabled type="text"class="group"style="width:100px" value ="'.$row["date_of_passing"].'"/>';
echo '</div>';
echo '</div>';
echo '</li>';
}
}
catch (mysqli_sql_exception $e) {
throw $e;
die();
}
}
/// You may call here record_list($mysqli) function as many times as you wish
record_list($mysqli)
$mysqli->close();
//close db connection