PHP error in mysql database selection

Question

I wrote a code in PHP to connect with Mysql database and add data into it.. code is given below:

$dbhostname = "localhost";
$dbusername = "root";
$dbpassword = "root";
$dbname = "rms_invoice";

function showDBMessage(){
    if($_POST["name"] != NULL){
        //came from register page
        if(register()){
            print("<br/>Registered successfully!!!");
        } else {
            print("<br/>Registration failed!!!");
        }
    }
}
function register(){
    global $dbhostname,$dbusername,$dbpassword,$dbname;
    // Create connection
    $con=mysqli_connect($dbhostname,$dbusername,$dbpassword);
    // Check connection
    if (!mysqli_connect_errno()) {
        print("MYSQL Connection established...<br/>");
        echo "<br/>Successful: ".mysqli_get_host_info($con);
        $selected = mysqli_select_db($con, $dbname);
        if(false!==$selected){
            $name = mysqli_real_escape_string($con, $_POST["name"]);
            $username = mysqli_real_escape_string($con, $_POST["username"]);
            $password = mysqli_real_escape_string($con, $_POST["password"]);
            $address = mysqli_real_escape_string($con, $_POST["address"]);

            $insertUserQuery="INSERT INTO USER(name,username,password,address) VALUES ('$name','$username','$password','$address')";
            echo $insertUserQuery;
            $result = mysqli_query($con, $insertUserQuery);
            if ( false===$result ) {
                printf("<br/>mysqli_connect_error: %s\n", mysqli_connect_error());
                printf("<br/>mysqli_error: %s\n", mysqli_error($con));
            } else {
                echo "<h4>New User Added!!!</h4><br/>";
                return true;
            }
        }else{
            printf("<br/>Error while selecting database, error:%s\n",mysqli_errno($con));
        }
    } else {
        print("<br/>Failed to connect to MySQL: "+mysqli_connect_error());
    }
    mysqli_close($con);
    return false;
}

and the output is:

MYSQL Connection established...
Successful: localhost via TCP/IP
INSERT INTO USER(name,username,password,address) VALUES ('nitin','ndthokare','p','beed')
mysqli_connect_error: 
mysqli_error: No database selected 
Registration failed!!!

It is getting connected but database selection seems to be problem. (same query executes successfully through mysql cli).

I tried many possible corrections in code discussed on SO, but could not succeed.

Can anybody help me to find out the mistake?

To be sure, "rms_invoice" is the correct database name, right? — John V.
– John V., Commented Apr 28, 2014 at 4:37
Please read this - php.net/manual/mysqli.quickstart.prepared-statements.php. Injecting values directly into your SQL statements is unsafe — Phil
– Phil, Commented Apr 28, 2014 at 5:05

Your Common Sense · Accepted Answer · 2014-04-28 04:41:21Z

2

 if(false!==!$selected){

is extremely unusual operator (called "double negative") means you want to execute the following code block only if $selected is FALSE. to make it much less confusing, write it without all these magic chants

 if($selected){

or even omit this useless check completely.

edited Apr 28, 2014 at 4:41

answered Apr 28, 2014 at 4:31

Your Common Sense

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5 Comments

AyB Over a year ago

Hmm, I do agree the double NOT is a definite weird but in actual that if block is getting executed, so this in itself cannot be the complete answer, maybe you should address more.

Phil Over a year ago

@ICanHasCheezburger The if block is being executed because $selected is FALSE meaning mysqli_select_db failed. This answer is completely correct

N D Thokare Over a year ago

Ya.. that was actually mistake by overlook... I it was if(false!==$selected) or if(true===!$selected)...

N D Thokare Over a year ago

but now the error is..

MYSQL Connection established... Successful: localhost via TCP/IP... Error while selecting database, error:1046 ... Registration failed!!!

Your Common Sense Over a year ago

that's quite obvious and self-explained one

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