Why isn't this working?

[V]

I created 1 function that connects to the db,

 

function dbConnect() {

$connection = new mysqli('localhost', 'user', 'password', 'gisttest')
or die ('Cannot open database');
return $connection;

}//end function

 

and another that queries some categories,

 

function listQuery($table) {

// prepare the SQL query
$sql = 'SELECT * FROM $table';

$result = $connection->query($sql) or die(mysqli_error());

// find out how many records were retrieved
$numRows = $result->num_rows;

while ($row = $result->fetch_assoc()) {
echo strtoupper("<li>{$row["cat_name"]}</li>");
}

}//end function

 

 

and I'm using

 

require_once("/functions/db_fns.php"); 

$connection = dbConnect();

echo listQuery("categories");

 

to show the results but I get

 

Notice: Undefined variable: connection in C:\wamp\www\gisttest\functions\db_fns.php on line 17

Fatal error: Call to a member function query() on a non-object in C:\wamp\www\gisttest\functions\db_fns.php on line 17

 

It works however when I establish the db connection within the listQuery fucntion and just echo it alone or if I add the entire connection code above echo listQuery("categories"); and remove the $connection = dbConnect(); on top. I have been trying different methods to combine both functions but I keep getting errors. Please someone help me figure this out  :'(

[Alex]

You should really look into variable scopes.

 

Your problem is that $connection is not defined within your function, listQuery(). One solution is to pass $connection as a parameter like so:

 

require_once("/functions/db_fns.php"); 

$connection = dbConnect();

echo listQuery("categories", $connection);

 

function listQuery($table, $connection) {

// prepare the SQL query
$sql = 'SELECT * FROM $table';

$result = $connection->query($sql) or die(mysqli_error());

// find out how many records were retrieved
$numRows = $result->num_rows;

while ($row = $result->fetch_assoc()) {
echo strtoupper("<li>{$row["cat_name"]}</li>");
}

}//end function

 

 

[V]

Ohh right, variable scopes! I read about them prior to starting to code but I guess I forgot. I tried the code you provided but there is still some sort of error. Not sure how to fix it..

 

Warning: mysqli_error() expects exactly 1 parameter, 0 given in C:\wamp\www\gisttest\functions\db_fns.php on line..

 

$result = $connection->query($sql) or die(mysqli_error());

 

 

[Alex]

You need to pass the connection, $connection in your case, to mysqli_error().

[V]

Ok sorry for being such a noob.. Now I'm not getting some scary errors.. First,

 

Table 'gisttest.$table' doesn't exist

 

I changed $table to the actual table name in the functions like so

 

function listQuery(categories, $connection) {

// prepare the SQL query
$sql = 'SELECT * FROM categories';

$result = $connection->query($sql) or die(mysqli_error($connection));

// find out how many records were retrieved
$numRows = $result->num_rows;

while ($row = $result->fetch_assoc()) {
echo $numRows;
echo strtoupper("<li>{$row["cat_name"]}</li>");
}


}//end function

 

Then I got

 

Parse error: parse error, expecting `'&'' or `T_VARIABLE' in C:\wamp\www\gisttest\functions\db_fns.php on line 12

 

so put a & in function listQuery(categories, $connection) { like this

 

function listQuery(categories&$connection) {

 

and I got

 

Fatal error: Cannot pass parameter 1 by reference in C:\wamp\www\gisttest\functions_test.php on line 17

 

so I tried removing the "categories" argument and just used $connection and got

 

Fatal error: Call to a member function query() on a non-object

 

Lastly, I decided that I suck at php.. lol

 

update: I tried putting back the $table arguments and vars but put $table in double quotes

 

$sql = 'SELECT * FROM "$table"';

 

and I get

 

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '"$table"' at line 1

 

I think I'm getting close..

 

[Alex]

Your first error is because single quotes don't have variable interpolation. Meaning that in this statement:

 

$sql = 'SELECT * FROM "$table"';

 

$table is being taken as a literal string, not a variable. So you need to do this:

 

$sql = "SELECT * FROM '$table'";

 

You're also forgetting a $ here:

 

function listQuery(categories, $connection) {

 

It should be:

 

function listQuery($categories, $connection) {

[V]

Thanks! I initially had the $ but somehow it got lost when I pasted the code

 

I used the double quotes and now it gives

 

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ''categories'' at line 1

 

I'm echoing this

 

echo listQuery("categories", $connection);

 

This is weird, not sure what I keep doing wrong

[Alex]

Well that's what I get for blindly looking at the code I guess. You don't need the single quotes there regardless.

 

$sql = "SELECT * FROM $table";

[V]

Thanks!! It's finally working! I will use your code as reference in many future projects ..and I should really learn more about functions before I get banished lol.