Database error: cannot use database mydatabase MySQL Error: 0 ()Session halted

Question

I have just download some code from a forum, however the code is not working well in mysql. It reports the following error:

Database error: cannot use database mydatabase MySQL Error: 0 ()Session halted.

I've already tried to find and fix in google in the error logs

Here is the code below:

<?php

class Database
{
    var $Host     = "127.0.0.1";        // Hostname of our MySQL server.
    var $Database = "mydatabase";               // Logical database name on that server.
    var $User     = "root";                 // User and Password for login.
    var $Password = "mypassword";

    var $Link_ID  = 0;                  // Result of mysqli_connect().
    var $Query_ID = 0;                  // Result of most recent mysqli_query().
    var $Record   = array();            // current mysqli_fetch_array()-result.
    var $Row;                           // current row number.
    var $LoginError = "";

    var $Errno    = 0;                  // error state of query...
    var $Error    = "";

    //-------------------------------------------
    //    Connects to the database
    //-------------------------------------------
    function connect()
    {
        if( 0 == $this->Link_ID )
            $this->Link_ID=mysqli_connect( $this->Host, $this->User, $this->Password );
        if( !$this->Link_ID )
            $this->halt( "Link-ID == false, connect failed" );
        if( !mysqli_query( sprintf( "use %s", $this->Database ), $this->Link_ID ) )
            $this->halt( "cannot use database ".$this->Database );
    }

    //-------------------------------------------
    //    Queries the database
    //-------------------------------------------
    function query( $Query_String )
    {
        $this->connect();
        $this->Query_ID = mysqli_query( $Query_String,$this->Link_ID );
        $this->Row = 0;
        $this->Errno = mysqli_errno();
        $this->Error = mysqli_error();
        if( !$this->Query_ID )
            $this->halt( "Invalid SQL: ".$Query_String );
        return $this->Query_ID;
    }

    //-------------------------------------------
    //    If error, halts the program
    //-------------------------------------------
    function halt( $msg )
    {
        printf( "<strong>Database error:</strong> %s", $msg );
        printf( "<strong>MySQL Error</strong>: %s (%s)", $this->Errno, $this->Error );
        die( "Session halted." );
    }

    //-------------------------------------------
    //    Retrieves the next record in a recordset
    //-------------------------------------------
    function nextRecord()
    {
        @ $this->Record = mysqli_fetch_array( $this->Query_ID );
        $this->Row += 1;
        $this->Errno = mysqli_errno();
        $this->Error = mysqli_error();
        $stat = is_array( $this->Record );
        if( !$stat )
        {
            @ mysqli_free_result( $this->Query_ID );
            $this->Query_ID = 0;
        }
        return $stat;
    }

    //-------------------------------------------
    //    Retrieves a single record
    //-------------------------------------------
    function singleRecord()
    {
        $this->Record = mysqli_fetch_array( $this->Query_ID );
        $stat = is_array( $this->Record );
        return $stat;
    }

    //-------------------------------------------
    //    Returns the number of rows  in a recordset
    //-------------------------------------------
    function numRows()
    {
        return mysqli_num_rows( $this->Query_ID );
    }

    //-------------------------------------------
    //    Returns the Last Insert Id
    //-------------------------------------------
    function lastId()
    {
        return mysqli_insert_id();
    }

    //-------------------------------------------
    //    Returns Escaped string
    //-------------------------------------------
    function mysqli_escape_mimic($inp)
    {
        if(is_array($inp))
            return array_map(__METHOD__, $inp);
        if(!empty($inp) && is_string($inp))
        {
            return str_replace(array('\\', "\0", "\n", "\r", "'", '"', "\x1a"), array('\\\\', '\\0', '\\n', '\\r', "\\'", '\\"', '\\Z'), $inp);
        }
        return $inp;
    }
    //-------------------------------------------
    //    Returns the number of rows  in a recordset
    //-------------------------------------------
    function affectedRows()
    {
        return mysqli_affected_rows();
    }

    //-------------------------------------------
    //    Returns the number of fields in a recordset
    //-------------------------------------------
    function numFields()
    {
        return mysqli_num_fields($this->Query_ID);
    }

}

?>

I have already tried other methods suggested on Stack Overflow.

Read https://www.php.net/manual/en/mysqli.query.php and check parameters in your code. — Georg Richter, Nov 11 '19 at 16:41
That's _your_ error message. Instead, let's see mysqli's error information. — Rick James, Nov 12 '19 at 00:01
Does database mydatabase exist? – Darragh Enright 2 days ago =yes — , Nov 13 '19 at 14:04
That's your error message. Instead, let's see mysqli's error information. – Rick James yesterday There is no other error message(logs) .. — , Nov 13 '19 at 14:05
Read php.net/manual/en/mysqli.query.php and check parameters in your code. – Georg Richter yesterday I already read it but I can't understand well. — , Nov 13 '19 at 14:05

score 0 · Accepted Answer · answered Nov 12 '19 at 13:49

From PHP Manual

Procedural style

mysqli_query ( mysqli $link , string $query [, int $resultmode = MYSQLI_STORE_RESULT ] ) : mixed

Parameters

link: A link identifier returned by mysqli_connect() query

query: The query string.

Your code can't work, since you pass a sql statement as first parameter, followed by the connection handle. Please note that you can also specify the database in mysqli_connect as 4th parameter. This will be faster, since the default database is set during the client server handshake.

Database error: cannot use database mydatabase MySQL Error: 0 ()Session halted

1 Answers1