Why does my code delete the first row from database - php

Question

i need your help. I have my delete all records button, when i delete all records it works fine until when i try to add records after the delete all, the first record will be deleted when i try to add the second record. i think the problem is because i never close my query after the delete all records.. i dont the exact syntax that can be used in my codes. please help me guys.
here is my code for delete all:
<?php
include_once 'connection.php';
$fname = $lname = $username = $phone = $email = $cemail = "";
$act="";
$txtid = 0;
if(isset($_GET['act'])){
$act=$_GET['act'];
if($act=='delete'){
$id=$_GET['id'];
$sql="delete from tbl_admin where id = $id";
$result = mysqli_query($conn,$sql)or die(mysqli_error());
if($result){
}
}
if($act=='deleteall'){
$sql="delete from tbl_admin";
$result = mysqli_query($conn,$sql)or die(mysqli_error());
}
if($act=='edit'){
$id=$_GET['id'];
$sql="select * from tbl_admin where id = $id";
$result = mysqli_query($conn,$sql)or die(mysqli_error());
while($row = mysqli_fetch_array($result)){
$txtid = $row['id'];
$fname = $row['fname'];
$lname = $row['lname'];
$username = $row['username'];
$phone = $row['mobileNo'];
$email = $row['email'];
}
}
if(isset($_POST['add'])){
// fname validate
if(empty($_POST["fname"])){
echo '<script> alert("first name is empty!"); </script>';
}else{
$fname = test_input($_POST["fname"]);
// lname validate
if(empty($_POST["lname"])){
echo '<script> alert("last name is empty!"); </script>';
}else{
$lname = test_input($_POST["lname"]);
//username
if(empty($_POST["username"])){
echo '<script> alert("username is empty!"); </script>';
}else{
$username = test_input($_POST["username"]);
//phone
if(empty($_POST["phone"])){
echo '<script> alert("mobile number is empty!!"); </script>';
}else{
$phone = test_input($_POST["phone"]);
//email
if(empty($_POST["email"])){
echo '<script> alert("email is empty!"); </script>';
}else{
$email = test_input($_POST["email"]);
//cemail
if(empty($_POST["cemail"])){
echo '<script> alert("confirm email is empty!"); </script>';
}else{
$cemail = test_input($_POST["cemail"]);
if($email != $cemail){
echo '<script> alert("Confirm Email!"); </script>';
}else{
$sql= "insert into tbl_admin(fname,lname,username,password,mobileNo,email,add_date) values('$fname','$lname','$username','123abc','$phone','$email',NOW())";
$result = mysqli_query($conn,$sql)or die(mysqli_error());
if($result){
echo '<script> alert("Successfully add admin user."); </script>';
$fname = $lname = $username = $phone = $email = $cemail = "";
}
}
}
}
}
}
}
}
}
if(isset($_POST['update'])){
if(empty($txtid)){
echo '<script>
alert("Select record to Update!");
</script>';
}else{
echo '<script>
alert("you can update record..");
</script>';
$fname = $lname = $username = $phone = $email = $cemail = "";
}
}
function test_input($data){
$data = trim($data);
$data = stripslashes($data);
$data = htmlspecialchars($data);
return $data;
}
?>

Answer 1

Because ALL your code exists inside this if statement
if(isset($_GET['act'])){
Then we have to assume that $_GET['act'] is always set to something
Because $_GET['act'] is always set to something then the DELETE code is getting run ALWAYS. Either its delete or deleteall
The code that rebuilds your web page is still missing, but basically you need to organise your code more logically, and also make sure that $_GET['act'] is only set when you actually want to do a delete, which would probably mean changing the HTML so it is not being left set.

Answer 2

I guess the methods are the same as it was in mysql (without i)
http://php.net/manual/en/mysqli-result.free.php
with non-object-oriented way it would be
mysqli_free_result($result);