Cannot select from table, but I can insert and create? - php

Question

I have this extremely weird issue with mysql. I can insert into, and create tables. However I cannot select anything and it does not display any error when I try, it just echos my line "Error: "
getDiff("validTable");
function getDiff($regNr) {
global $servername, $username, $password, $dbname;
// Create connection
$conn = new mysqli($servername, $username, $password, $dbname);
// Check connection
if ($conn->connect_error) {
die("Connection failed: " . $conn->connect_error);
}
//todo
$sql = "SELECT * FROM $regNr ORDER BY id LIMIT 1";
$result = $conn->query($sql);
if ($result === TRUE) {
echo "done";
} else {
$error = $result->error;
echo "Error: " . $error;
}
$conn->close();
}
But when I insert to the DB using this
$query = "CREATE TABLE IF NOT EXISTS $regNr ( `id` MEDIUMINT NOT NULL AUTO_INCREMENT, `mail` INT NOT NULL , `price` INT NOT NULL , `views` INT NOT NULL , `the_date` DATE NOT NULL , `time` VARCHAR(5) NOT NULL, PRIMARY KEY (id) )";
runQuery($query);
function runQuery($todo) {
global $servername, $username, $password, $dbname;
// Create connection
$conn = new mysqli($servername, $username, $password, $dbname);
// Check connection
if ($conn->connect_error) {
die("Connection failed: " . $conn->connect_error);
}
//todo
$sql = $todo;
if ($conn->query($sql) === TRUE) {
echo "done";
} else {
echo "Error: " . $conn->error;
}
$conn->close();
}
It works just fine and dandy. WHAT HAVE I DONE WRONG?! This is driving me crazy!

Answer 1

It shows only "Error" because your query succeeds and returns a mysql object which is not equal to True and therefore it does not echo done
See (http://php.net/manual/en/mysqli.query.php)
Returns FALSE on failure. For successful SELECT, SHOW, DESCRIBE or
EXPLAIN queries mysqli_query() will return a mysqli_result object. For
other successful queries mysqli_query() will return TRUE.
Change your code with the code below to make it work:
if ($conn->query($sql) === FALSE) {
echo "Error: " . $conn->error;
} else {
echo "done";
}
Basically turning the if around such that it checks for FALSE or not FALSE.
Most probably you also want to store the result in a variable like:
if ($result = $conn->query($sql) === FALSE) {
And later on use $row = $result->fetch_array() or $row = $result_fetch_assoc() to get the data.

Answer 2

mysqli_query
Returns FALSE on failure. For successful SELECT, SHOW, DESCRIBE or
EXPLAIN queries mysqli_query() will return a mysqli_result object. For
other successful queries mysqli_query() will return TRUE.
As per this condition
if ($conn->query($sql) === TRUE) {
You get mysqli_result from your query and this is not equal to TRUE and you always goes into error condition
To fetch data from query use fetch_array
$row = $result->fetch_array(MYSQLI_NUM);
printf ("%s (%s)\n", $row[0]);
To get error form query we use $conn->error not $result->error it need your connection variable not your result variable
Read http://php.net/manual/en/mysqli.error.php