Test whether the database connection success

? <php
    echo "Hello Word <br>"; // test could not be resolved php code
    echo date ( 'Ymd H: i : s'); // time of test development environment does not
    echo '<br>';
    / address database service account password database name / four parameters of the database
    $ db = new new MySQLi ( 'localhost', 'root', 'root', 'z_0222');
    ! mysqli_connect_error () or Die ( 'database connection failed'); // If the database connection error given
    $ db-> query ( 'set names utf8'); // set the format database UTF8
   
　　// var_dump ($ DB); // can not be connected to the test database, the database is a printing

    $ sql = 'select * from student'; // sql statement
    $ result = $ db-> query ( $ sql); // sql statement execution, additions and deletions to which it
　　// if ($ result) {// If successful statement CRUD
　　// echo 'successfully executed';// output successfully executed
　　//}
    // If query, returns the resources, the resources need to be converted into identification data php
    $ ARR = $ result-> fetch_all ();
    echo '<pre>'; // to pre format
    var_dump ($ arr); // there is no test data, the print data
    echo '</ pre>';
?>