PHP Insert Query Using Prepare Statement - php

Question

I have created an insert form. I'm doing an insertion operation into MySQL using prepare statement but it's not working. I don't understand what's wrong. Please help me to solve this issue. Is this what I did correct?
insert.php
<?php
include('dbconn.php');
session_start();
$_SESSION['example']='Session Created';
$srn = $_POST['srn'];
$client = $_POST['client']; // required
$category = $_POST['category'];
$sd = $_POST['sd']; // required
$fd = $_POST['fd'];
$host = "localhost";
$user = "root";
$pwd = "root";
$db = "eservice";
$pdo = new PDO("mysql:host=$host;dbname=$db", $user, $pwd);
$sql = "Insert into main(client,category,sd,fd) values(:client,:category,:sd,:fd)";
$stmt = $pdo->prepare($sql);
$stmt->bindParam(':client',$_POST['client'],PDO::PARAM_STR);
$stmt->bindParam(':category',$_POST['category'],PDO::PARAM_STR);
$stmt->bindParam(':sd',$_POST['sd'],PDO::PARAM_STR);
$stmt->bindParam(':fd',$_POST['fd'],PDO::PARAM_STR);
$stmt->execute();
?>
dbconn.php
<?php
$host = "localhost";
$user = "root";
$pwd = "root";
$db = "eservice";
$mysqli = new mysqli($host,$user,$pwd,$db);
/* ESTABLISH CONNECTION */
if (mysqli_connect_errno()) {
echo "Failed to connect to mysql : " . mysqli_connect_error();
exit();
}
?>

Answer 1

Its always good to put up the errors you are having.
You are using two different database connection types pdo, and mysqli. You only need one.
I stripped your code down to the minimum.
<?php
$host = "localhost";
$user = "root";
$pwd = "root";
$db = "eservice";
$pdo = new PDO("mysql:host=$host;dbname=$db", $user, $pwd);
//$srn = $_POST['srn'];
$client = $_POST['client']; // required
$category = $_POST['category'];
$sd = $_POST['sd']; // required
$fd = $_POST['fd'];
// make sure client and sd are set here
$stmt = $pdo->prepare("
INSERT INTO
main
(client,category,sd,fd)
VALUES
(:client,:category,:sd,:fd)
");
$success = $stmt->execute([
'client' => $client,
'category' => $category,
'sd' => $sd,
'fd' => $fd
]);