Cannot query MySQL database via PHP - php

Question

In my PHP code, i'm easily writing records to my database but for some reason i can't read anythign out. My PHP code is:
$conn = new mysqli($servername, $username, $password, $dbname);
// Check connection
if ($conn->connect_error) {
die("Connection failed: " . $conn->connect_error);
}
$sql = "SELECT * FROM companies";
if ($conn->query($sql) === TRUE)
{
echo "query success";
while($row = $result->fetch_assoc())
{
echo "ID: " . $row["ID"]. " - Name: " . $row["name"]. "<br>";
}
}
else
{
echo "query failure";
echo "Error: " . $sql . "<br>" . $conn->error;
}
$sql = "INSERT INTO companies (name)
VALUES ('mycompany')";
if ($conn->query($sql) === TRUE)
{
echo "insert success";
}
else
{
echo "insert failure";
echo "Error: " . $sql . "<br>" . $conn->error;
}
The output I get from the browser when i run it is:
query failureError: SELECT * FROM companies
insert success
I've tried variations of apostrophes, carets, quotes in that $sql string. I've tried running this query in HeidiSQL and it works fine. Any ideas where I'm going wrong? Any suggestions of more basic stuff I can try to narrow down the source of the problem?
thanks!

Answer 1

Using mysqli->query() with a SELECT statement returns an instance of mysqli_result. It is not identical to true (=== true), but nor does it represent an error.
Moreover, $result is undefined.
Use this instead:
$conn = new mysqli($servername, $username, $password, $dbname);
// Check connection
if ($conn->connect_error) {
die("Connection failed: " . $conn->connect_error);
}
$sql = "SELECT * FROM companies";
if (($result = $conn->query($sql)) !== FALSE)
{
echo "query success";
while($row = $result->fetch_assoc())
{
echo "ID: " . $row["ID"]. " - Name: " . $row["name"]. "<br>";
}
}
else
{
echo "query failure";
echo "Error: " . $sql . "<br>" . $conn->error;
}
...
This simply changes your === TRUE check to !== FALSE. MySQLi::query() returns boolean FALSE on failure, boolean TRUE on a successful query without result sets or a mysqli_result upon success with a result set.
This also assigns the result of query() into $result.

Answer 2

You have not assign the query result to $result variable.
$conn = new mysqli($servername, $username, $password, $dbname);
// Check connection
if ($conn->connect_error) {
die("Connection failed: " . $conn->connect_error);
}
$sql = "SELECT * FROM companies";
$result = $conn->query($sql);
if ($result === TRUE)
{
echo "query success";
while($row = $result->fetch_assoc())
{
echo "ID: " . $row["ID"]. " - Name: " . $row["name"]. "<br>";
}
}
else
{
echo "query failure";
echo "Error: " . $sql . "<br>" . $conn->error;
}
$sql = "INSERT INTO companies (name)
VALUES ('mycompany')";
if ($conn->query($sql) === TRUE)
{
echo "insert success";
}
else
{
echo "insert failure";
echo "Error: " . $sql . "<br>" . $conn->error;
}

Answer 3

The problem is that a SELECT query will return a mysqli_result object on SUCCESS not a boolean TRUE. Only if the query fails, will it return a boolean FALSE;
Therefore you should use it like this :
$result = $conn->query($sql);
if ($result !== FALSE){
while($row = $result->fetch_assoc())
{
echo "ID: " . $row["ID"]. " - Name: " . $row["name"]. "<br>";
}
}

Answer 4

just change your if condition :-
if ($result = $conn->query($sql))
{
echo "query success";
while($row = $result->fetch_assoc())
{
echo "ID: " . $row["id"]. " - Name: " . $row["name"]. "<br>";
}
}