Use $query="SELECT"... in a function() - php

Question

I want to use a MySQL Query in a function to retrieve information from a table:
function selectFromMemTable($a) {
$query="SELECT * FROM members WHERE username = '" . $a ."'";
$result = mysql_query($query) or die ("FOUT: " . mysql_error());
while (list($id, $a, $b, $c, $d, $e, $f) = mysql_fetch_row($result)){
$user_id = $id;
$user_usernaam = $a;
$user_voornaam = $b;
$user_achternaam = $c;
$user_email = $d;
$user_password = $e;
$user_admin = $f;
}
}
In the script I want to use the following code to retrieve the $user_id.
selectFromMemTable(username);
echo $user_id;
When loading page I receive the following error:
Fatal error: Call to undefined function selectFromTable() in test.php on line 28
Without the function it works correctly. What is the problem?
Sorry, the correct script is:
selectFromMemTable($_COOKIE["user"]);
echo $user_id;

Answer 1

You named your function selectFromMemTable but are calling selectFromTable. That's the wrong name.

Answer 2

Check the name of your function. The comiler says you try to call a function with a different name.
In your function selectFromMemTable you should return the selected values or global the vars. Because you cannot access them until they are private only.
Never trust incoming request vars! Yo should escape $_COOKIE["user"] for use in databse query (use mysql_real_escape_string or the newer mysqli_real_escape_string).
Since there matches only 1 user per username you should LIMIT the selected rows to 1.
Be aware of using the username directly from cookie to access private userdata. For security reasons you should use a individual session ID or a cryptographic stronger individual qualifier for use with cookies. That's because actually the user can change it's name in the cookie value and than he's logged in as another user.
You can fetch an assoc - it's easyer to access and you don't need to set tons of variables.
Function declaration:
function selectFromMemTable($a)
{
$query = sprintf("SELECT * FROM members WHERE username = '%s' LIMIT 1",
mysql_real_escape_string($a));
$result = mysql_query($query) or die ("FOUT: " . mysql_error());
return mysql_fetch_assoc($result);
}
Use the function:
$user = selectFromMemTable($_COOKIE["user"]);
if(!$user)
echo "no user";
else
echo $user['id'];
Edit: Maybe you have to change the id in $user['id'] to the right column name.