How to change mysql to mysqli?


Question

Based on this code below I use for regular mysql, how could I convert it to use mysqli?

Is it as simple as changing **mysql _query($sql); to mysqli _query($sql); ?**

<?PHP

//in my header file that is included on every page I have this
$DB["dbName"] = "emails";
$DB["host"] = "localhost";
$DB["user"] = "root";
$DB["pass"] = "";
$link = mysql_connect($DB['host'], $DB['user'], $DB['pass']) or die("<center>An Internal Error has Occured. Please report following error to the webmaster.<br><br>".mysql_error()."'</center>");
mysql_select_db($DB['dbName']);
// end header connection part

// function from a functions file that I run a mysql query through in any page.
function executeQuery($sql) {
    $result = mysql_query($sql);
    if (mysql_error()) {
        $error = '<BR><center><font size="+1" face="arial" color="red">An Internal Error has Occured.<BR> The error has been recorded for review</font></center><br>';
        if ($_SESSION['auto_id'] == 1) {
            $sql_formatted = highlight_string(stripslashes($sql), true);
            $error .= '<b>The MySQL Syntax Used</b><br>' . $sql_formatted . '<br><br><b>The MySQL Error Returned</b><br>' . mysql_error();
        }
        die($error);
    }
    return $result;
}

// example query ran on anypage of the site using executeQuery function
$sql='SELECT auto_id FROM friend_reg_user WHERE auto_id=' .$info['auto_id'];
$result_member=executequery($sql);
if($line_member=mysql_fetch_array($result_member)){
    extract($line_member);
} else {
    header("location: index.php");
    exit;
}
?>
1
49
12/13/2017 1:56:24 PM

Accepted Answer

The first thing to do would probably be to replace every mysql_* function call with its equivalent mysqli_*, at least if you are willing to use the procedural API -- which would be the easier way, considering you already have some code based on the MySQL API, which is a procedural one.

To help with that, the The MySQLi Extension Function Summary is definitely something that will prove helpful.

For instance:

Note: For some functions, you may need to check the parameters carefully: Maybe there are some differences here and there -- but not that many, I'd say: both mysql and mysqli are based on the same library (libmysql ; at least for PHP <= 5.2)

For instance:

  • with mysql, you have to use the mysql_select_db once connected, to indicate on which database you want to do your queries
  • mysqli, on the other side, allows you to specify that database name as the fourth parameter to mysqli_connect.
  • Still, there is also a mysqli_select_db function that you can use, if you prefer.


Once you are done with that, try to execute the new version of your script... And check if everything works ; if not... Time for bug hunting ;-)

70
4/12/2019 3:15:00 PM

(I realise this is old, but it still comes up...)

If you do replace mysql_* with mysqli_* then bear in mind that a whole load of mysqli_* functions need the database link to be passed.

E.g.:

mysql_query($query)

becomes

mysqli_query($link, $query)

I.e., lots of checking required.


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