PHP database connection file including?

My conn.php file is here..

<?php $username="root"; $password=""; $server="127.0.0.1"; $db="login1"; $conn=new mysqli($server,$username,$password,$db); if(!$conn){ echo "Connection not established"; } ?> 

login1 is the database name or the table name, or both?

Instead of:

if(!$conn){ echo "Connection not established"; } 

Do:

if ($conn->connect_errno) { printf("Connect failed: %s\n", $conn->connect_error); exit(); } 

As suggested in the documentation. And return the error here.

ok But this code does give result ....any mistake here?

$sql="SELECT * FROM login1 WHERE L1='$uname'"; $result=$conn->query("$sql"); if($result){ echo("welcome to new page"); } else { echo ("login problem"); } 

It seems fine, the only problem I can see is related to the space between the include and the string:

include"conn.php"; 

It should be:

include "conn.php"; 

But at query level use $result->error:

if($result){ echo "welcome to new page"; } else{ echo $result->error; } 

It will display the error related to the query, if any.

 if($result->num_rows==true){ echo("welcome"); } else { echo ("invalid username"."<br>"); } 

I have
solved with that code...its ok?

Mysqli num_rows returns integers not booleans (true|false) so if you want to check how many rows you're returning change the if statement to:

if($result->num_rows > 0){ 

But, if the query fails for an error this statement will not prevent a PHP notice:

PHP Notice: Trying to get property of non-object ... 

It happens because $result will be false, so a more complete check is to verify if $result is not false:

if($result && $result->num_rows > 0){ 

Note that mysqli_query on success can return an object or simply boolean true, the documentation explains the cases:

Returns FALSE on failure. For successful SELECT, SHOW, DESCRIBE or EXPLAIN queries mysqli_query() will return a mysqli_result object. For other successful queries mysqli_query() will return TRUE.

So for SELECT queries you can almost always rely on num_rows but if you perform an INSERT, DELETE or UPDATE then you cannot use num_rows, this for example:

$result = $mysqli->query("create temporary table mytest engine = memory as select 1+1 as 'sum' from dual"); 

Is a perfect valid query, it's the equivalent of an INSERT ... SELECT, and it will create a temporary table, but it will not return an object, it will return only boolean, so this check:

if($result && $result->num_rows > 0) 

Will fail generating the same PHP notice as above, in this case use only:

if($result) 

Edit: adding info
I forgot to add an exception: a select query can return only boolean true if you use the statement SELECT ... INTO to assign variables or write to a file, as example:

$result = $mysqli->query("select 1+1 as 'sum' from dual into @sum");