Updating DB data from PHP variables - php

Question

I have a problem with variables in an SQL Statement. I have a form where a user can update his profile. The form redirects to action.php?action=settings
When I try without $variables, there is no problem! But the thing is, I have a lot of queries like this, but not for updating.
function change_user_data($trainer) {
require("database.php");
try {
$results = $db->query("UPDATE trainer SET email='$email', status='$status', password='$password' WHERE name='$trainer'");
} catch (Exception $e) {
echo "Data could not be changed!";
exit;
}
}
and this is my action.php
if ($action == "settings") {
$email = $_POST['email'];
$status = $_POST['status'];
$password = $_POST['password'];
change_user_data($trainer);
}
When I echo those $variables, they get displayed so they are not empty. But this query updates my table but with no data, so everything is empty afterwards.

Answer 1

I think the problem is variable scope.
Variables defined outside of function cannot use in function except global variable or something.
You have two method.
First. If change_user_data function is in action.php file, add "global $email, $status, $password" like this:
function change_user_data($trainer) {
global $email, $status, $password;
require("database.php");
try {
$results = $db->query("UPDATE trainer SET email='$email', status='$status', password='$password' WHERE name='$trainer'");
} catch (Exception $e) {
echo "Data could not be changed!";
exit;
}
}
Or second. Pass the email, status, password data to function. Then you can use it.
Please check this manual:
http://php.net/manual/en/language.variables.scope.php

Answer 2

you can try this:
$results = $db->query("UPDATE trainer SET email='".$email."', status='".$status."', password='".$password."' WHERE name='".$trainer."'");

Answer 3

change_user_data($trainer, $email, $password, $status);
function change_user_data($trainer, $email, $password, $status) {
require("database.php");
try {
$results = $db->query("UPDATE trainer SET email='$email', status='$status', password='$password' WHERE name='$trainer'");
} catch (Exception $e) {
echo "Data could not be changed!";
exit;
}
}

Answer 4

After You Gettings Post varibles Then Check For those variables
whether those are empty or not
if not empty or NULL Then Update Database with Update Query With Non empty Variables

Answer 5

May be
Wrong data type of your columns. Check your table structure carefully. Example: if you set you column email as int then you cannot insert or update it's row value as text or letter
Incorrect variables inside single quote. Try to concatenate variable and query string for better practice
If those don't work
Try to make mysql syntax error and check values of those variables, then you can define the error.
Sorry for my bad english

Answer 6

You have few problems with this function:
Scoping issue, you did not pass all values
You are vulnerable to sql injection
You dont check if the record is updated
function:
function change_user_data($db, $params) {
try {
$sql = "UPDATE trainer SET email= ?, status=?, password=? WHERE name=?";
$stmt = $db->prepare($sql);
$stmt->execute($params);
$success = ($stmt->rowCount() > 0) ? true : false;
} catch (Exception $e) {
echo "Data could not be changed!";
$success = false;
}
return $success;
}
Usage
require("database.php");
$params = array($trainer, $email, $password, $status);
$user_data_updated = change_user_data($db, $params);
if($user_data_updated){
echo 'user data updated';
}else{
echo 'user data did not update';
}