php- inserting data into the database - php

Question

I am a beginner when we talk about PHP. SO I have no idea where I made a mistake using PHP.
<?php
require "conn.php";
$name = "yolo";
$surname = "yolo";
$nameOfFee= "asd";
$date = '2012-08-06';
$mysql_query = "(INSERT INTO Relation (Person_ID, Fee_ID, Date_of_fee)
SELECT Person.ID,Fee.ID,'$date'
FROM Person,Fee
WHERE Person.Name = '$name' AND Person.Surname = '$surname' AND Fee.Name_of_fee = '$nameOfFee');";
if($conn->query($mysql_query) === TRUE){
echo "Insert completed";
}
else{
echo "Insert not completed";
}
$conn->close();
?>
It always puts that Insert is not complete...

Answer 1

The Problems
There are a few syntax errors in this piece of code you have provided:
// here it starts, what is this "(" for before insert?
// Take note that your query is vulnerable to SQL attacks
$mysql_query = "(INSERT INTO Relation (Person_ID, Fee_ID, Date_of_fee)
SELECT Person.ID,Fee.ID,'$date'
FROM Person,Fee
WHERE Person.Name = '$name' AND Person.Surname = '$surname' AND Fee.Name_of_fee = '$nameOfFee');";
How to fix it
To fix these things I recommend you use the MySQLi OOP, like you are using now, but add prepared statements. I will walk through the new code with you so you can understand the process.
require "conn.php";
$name = "yolo";
$surname = "yolo";
$nameOfFee= "asd";
$date = '2012-08-06';
$sql = "INSERT INTO Relation (Person_ID, Fee_ID, Date_of_fee) VALUES (?, ?, ?)"; // rewrite your query with a preset number of values to prevent SQL Attacks
if($stmt = $conn->prepare( $sql ))
{ // before we run check to make sure the query worked
$stmt->bind_param('sss', $name, $nameOfFee, $date); // bind your variables so to know what goes where
$stmt->execute(); // execute the query
$stmt->close(); // close connection for safety
// message as an array for the user as feedback.
$message = array(
'is_error' => 'success',
'message' => 'Record was entered into database.'
);
}
else
{
$message = array(
'is_error' => 'danger',
'message' => 'Query Error, please revise the information.'
);
}