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  1. #1
    New to the CF scene
    Join Date
    Jun 2010
    Thanked 0 Times in 0 Posts

    Issues with classes: mysqli_query() expects parameter 1 to be mysqli, null given

    Hello everyone!

    I am having trouble the last few days trying to output data from my database. This is concerning using the "mysqli_connect" and "mysqli_query" parameters.

    What I have done is I want to put the connection settings in a class, and I with the normal "mysql_connect" it does work. But with mysqli it doesn't work.

    What I get is an error message saying: "Warning: mysqli_query() expects parameter 1 to be mysqli, null given". Is there anything I am doing wrong here?

    PHP Code:
    class database_connect {
    connect() {
    $connect_db mysqli_connect($this->db_host$this->db_user$this->db_pass$this->db_db) or die ("Connection failed");
    close() {

    $db_countries = new database_connect;
    $db_countries->db_host "localhost";
    $db_countries->db_user "root";
    $db_countries->db_pass "";
    $db_countries->db_db "site_countries";

    dbconnect_countries() {
    $query "SELECT * FROM countries";
    $result mysqli_query($connect_db$query) or die ("Error in query: $query. ".mysqli_error());
        if (
    mysqli_num_rows($result) > 0) {
    $row mysqli_fetch_row($result)) {
        else {
    '<div>No countries found!</div>';

    Any help would be appreciated!


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  3. #2
    Senior Coder
    Join Date
    Jul 2011
    Thanked 171 Times in 171 Posts
    You're not really displaying an understanding of variable scope. You should avoid trying to global scope variables and connection pointers. You also don't seem to understand how classes work. You know you can use mysqli as an object itself?

    When you call a new instance of a class, the object will call the construct() magic method. I would use this to connect to the database, or at least set the connection parameters (although an immediate connection avoids actually storing the values). I would then store the connection pointer in a property of the class. The class should also store methods to act on the connection.

    Classes and objects are used to handle specific areas - separating logic into classes that deal with similar tasks. Therefore, a database class should be built to contain all the tools to access the database.

    How I would build your database class:
    PHP Code:
    class database {

    $connection '';

        protected function 
    $this->connection mysqli_connect($host$db_user$db_pass$database);
                throw new 
    Exception('Connect failed: '.mysqli_error());

        protected function 
    // Could probably throw an exception here as well, if result was false
    return mysqli_query($this->connection$query);


    Google some database class examples - the php.net manual has a great explanation of PHP class definitions.
    Useful function to retrieve difference in times
    The best PHP resource
    A good PHP FAQ
    PLEASE remember to wrap your code in [PHP] tags.
    PHP Code:
    // Replace this
    // With this
    // Then check for values/forms. Some IE versions don't send the submit button 
    Always code as if the guy who ends up maintaining your code will be a violent psychopath who knows where you live.


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