MySQL event not working (insert statement) - mysql

Question

I am using PHP to execute the SQL query, the event can be created but no random data is inserted into the database. The global event scheduler is set on.
Is there anything wrong with my code?
What I try to do is to insert random data into the database every second once the event is created.
Below are my code :
<?php
$hostname="localhost";
$username="root";
$password='xxx';
$dbname="database";
$conn= mysqli_connect($hostname,$username,$password,$dbname);
if (mysqli_connect_errno($conn)) {
echo "Failed to connect to database: " . mysqli_connect_error();
}
else {
$query="CREATE EVENT XXX
ON SCHEDULE
EVERY 1 SECOND
STARTS '2019-12-28 9:45:20' ON COMPLETION PRESERVE ENABLE
DO
INSERT INTO water(Id,datetime,ph1,ec1,wt1,
ph2,ec2,wt2,
ph3,ec3,wt3,
ph4,ec4,wt4)
VALUES(NOW(),ROUND(FLOOR(21 * RAND()) / 100, 2) + 7.40,
ROUND(FLOOR(101 * RAND()) / 10, 1) + 650,
ROUND(FLOOR(21 * RAND()) / 10, 1) + 23,
ROUND(FLOOR(21 * RAND()) / 100, 2) + 7.40,
ROUND(FLOOR(101 * RAND()) / 10, 1) + 650,
ROUND(FLOOR(21 * RAND()) / 10, 1) + 23,
ROUND(FLOOR(21 * RAND()) / 100, 2) + 7.40,
ROUND(FLOOR(101 * RAND()) / 10, 1) + 650,
ROUND(FLOOR(21 * RAND()) / 10, 1) + 23,
ROUND(FLOOR(21 * RAND()) / 100, 2) + 7.40,
ROUND(FLOOR(101 * RAND()) / 10, 1) + 650,
ROUND(FLOOR(21 * RAND()) / 10, 1) + 23);";
if(mysqli_query($conn, $query)){
echo "successful";
}else{
echo ("error :". mysqli_error($conn));
}
}
mysqli_close($conn);
?>