php echo result from mysql and datetime selection - php

Question

MySQL database Start = "2017-03-29 01:30:00"
The problem is:
I print the $SQL and search the record in MySQL database, it can search the record. However, I need to debug and test if there is no result, it will be expected to echo "No". But, it always to echo "Yes" no matter I can get the record in MySQL or not.
How can I fixed it.
Main purpose: Get the record if there are and Echo "No" if there don't have record
<?php
$serverName = "localhost";
$username = "root";
$password = "";
$dbName = "fyp";
$tbName = "events";
$String_start = '2017-03-29 01:28:00';
$String_end = '2017-03-29 01:32:00';
$conn = new mysqli($serverName, $username, $password, $dbName);
if ($conn->connect_error) {
die("Connection failed: " . $conn->connect_error);
}
//$staffID = $_SESSION['userID'];
$staff_ID = '15207800';
$sql = "SELECT *
FROM `$tbName`
WHERE `start` BETWEEN ('$String_start') AND ('$String_end')";
echo $sql;
$result=mysqli_query($conn,$sql);
if($result)
{
echo "Yes";
}
else{
echo "no";
}
?>

Answer 1

Mysql query only return fails if there is an issue, for successful execution it returns TRUE even if there is no record. You can achieve with follwing way
<?php
$serverName = "localhost";
$username = "root";
$password = "";
$dbName = "fyp";
$tbName = "events";
$String_start = '2017-03-29 01:28:00';
$String_end = '2017-03-29 01:32:00';
$conn = new mysqli($serverName, $username, $password, $dbName);
if ($conn->connect_error) {
die("Connection failed: " . $conn->connect_error);
}
//$staffID = $_SESSION['userID'];
$staff_ID = '15207800';
$sql = "SELECT *
FROM `$tbName`
WHERE `start` BETWEEN ('$String_start') AND ('$String_end')";
echo $sql;
$result=mysqli_query($conn,$sql);
$num_rows = mysqli_num_rows($result);
if($num_rows > 0)
{
echo "Yes";
}
else{
echo "no";
}
?>

Answer 2

Use mysqli_num_rows that will return total results returned by the query. If total > 0 then results found else no results.
To fetch rows from MySQL result set, use mysqli_fetch_assoc
$result = mysqli_query($conn,$sql);
// $result contains result set and will return `TRUE` if query was successfully executed
// and will return `FALSE` only in case of error
$total = mysqli_num_rows($result);
if($total > 0)
{
echo "Yes";
// Fetch rows from mysql result set
while($row=mysqli_fetch_assoc($result))
{
print_r($row);
}
}
else
{
echo "no";
}