For User before Update - php

Question

I have made an API to insert data of 7 fields (fullname, city, bloodgroup, password, mobileno, lastdonated, created_date) in a mysql database using INSERT, please help me to add some code to search if the user is already added using the mobileno field and only then add the record else show the message "User already exists".
<?php
header("Access-Control-Allow-Origin: *");
header("Content-Type: application/json; charset=UTF-8");
if(count($_REQUEST) > 0)
{
$conn = mysqli_connect("localhost", "creative_bloodapp", "PasSwORd", 'creative_bldapp');
$fullname =$_POST['fullname'];
$city =$_POST['city'];
$bloodgroup =$_POST['bloodgroup'];
$password =$_POST['password'];
$mobileno =$_POST['mobileno'];
$lastdonated =$_POST['lastdonated'];
$created_date = date('Y-m-d H:i:s');
$sql = "INSERT INTO register (fullname, city, bloodgroup, password, mobileno, lastdonated, created_date) VALUES ('" . $fullname . "','" . $city . "','" . $bloodgroup . "','" . $password . "','" . $mobileno . "','" . $lastdonated . "','". $created_date . "');";
$qur = $conn->query($sql);
if($qur){
$query="SELECT * FROM register ORDER BY mobileno DESC LIMIT 1;";
$data=array();
$result=mysqli_query($conn, $query);
$row=mysqli_fetch_assoc($result);
mysqli_close($conn);
response(1,"User has been registered!",$row);
}else{
mysqli_close($conn);
response(0,"Not Registered!",NULL);
}
}
else
{
response(0,"Not Registered!",NULL);
}
function response($status,$status_message,$data)
{
header("HTTP/1.1 ".$status);
$response['status']=$status;
$response['status_message']=$status_message;
$response['data']=$data;
$json_response = json_encode($response);
echo $json_response;
}
?>

Answer 1

Looking for something like this; I changed some queries and re-wrote a part for you. Also added mysqli_real_escape_string.
<?php
header("Access-Control-Allow-Origin: *");
header("Content-Type: application/json; charset=UTF-8");
if(count($_REQUEST) > 0)
{
$conn = mysqli_connect("localhost", "creative_bloodapp", "PasSwORd", 'creative_bldapp');
$fullname = mysqli_real_escape_string($conn, $_POST['fullname']);
$city = mysqli_real_escape_string($conn, $_POST['city']);
$bloodgroup = mysqli_real_escape_string($conn, $_POST['bloodgroup']);
$password = mysqli_real_escape_string($conn, $_POST['password']);
$mobileno = mysqli_real_escape_string($conn, $_POST['mobileno']);
$lastdonated = mysqli_real_escape_string($conn, $_POST['lastdonated']);
$created_date = date('Y-m-d H:i:s');
$query="SELECT * FROM register WHERE mobileno = '".$mobileno."'";
$qur=mysqli_query($conn, $query);
if(count(mysqli_num_rows($qur) !== 0)){
$data=array();
$result=mysqli_query($conn, $query);
$row=mysqli_fetch_assoc($result);
mysqli_close($conn);
response(1,"User has been registered!",$row);
}else{
$sql = "INSERT INTO register (fullname, city, bloodgroup, password, mobileno, lastdonated, created_date) VALUES ('" . $fullname . "','" . $city . "','" . $bloodgroup . "','" . $password . "','" . $mobileno . "','" . $lastdonated . "','". $created_date . "');";
$qur=mysqli_query($conn, $query);
mysqli_close($conn);
response(0,"Not Registered!",NULL);
}
}
else
{
response(0,"Not Registered!",NULL);
}
function response($status,$status_message,$data)
{
header("HTTP/1.1 ".$status);
$response['status']=$status;
$response['status_message']=$status_message;
$response['data']=$data;
$json_response = json_encode($response);
echo $json_response;
}

Answer 2

Yes, Make it mobileno unique key so
if($qur)
{
// new mobileno
//add it will take
}
else
{
// repeated i will not accept, you put mobileno exist.
}

Answer 3

<?php
header("Access-Control-Allow-Origin: *");
header("Content-Type: application/json; charset=UTF-8");
if(count($_REQUEST) > 0)
{
$conn = mysqli_connect("localhost", "creative_bloodapp", "PasSwORd", 'creative_bldapp');
$fullname = mysqli_real_escape_string($conn, $_POST['fullname']);
$city = mysqli_real_escape_string($conn, $_POST['city']);
$bloodgroup = mysqli_real_escape_string($conn, $_POST['bloodgroup']);
$password = mysqli_real_escape_string($conn, $_POST['password']);
$mobileno = mysqli_real_escape_string($conn, $_POST['mobileno']);
$lastdonated = mysqli_real_escape_string($conn, $_POST['lastdonated']);
$created_date = date('Y-m-d H:i:s');
$verifysql = "select id from register where mobileno='".$mobileno."'";
$qur = $conn->query($verifysql);
if($qur->num_rows == 0){
$sql = "INSERT INTO register (fullname, city, bloodgroup, password, mobileno, lastdonated, created_date) VALUES ('" . $fullname . "','" . $city . "','" . $bloodgroup . "','" . $password . "','" . $mobileno . "','" . $lastdonated . "','". $created_date . "');";
$result = $conn->query($sql);
if($result){
mysqli_close($conn);
response(200,"User has been registered!",$row);
}else{
mysqli_close($conn);
response(500,"Registeration Failed",NULL);
}
}
else{
mysqli_close($conn);
response(409,"User Already Exists!",NULL);
}
}
else
{
response(400,"Not Registered!",NULL);
}