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

Answer 1

Here is a complete tutorial how to make it quickly if you need to make worgking again a website after PHP upgrade. I used it after upgrading hosting for my customers from 5.4 (OMG!!!) to 7.x PHP version.

This is a workaround and it is better to rewrite all code using PDO or mysqli Class.

1. Connection definition

First of all, you need to put the connection to a new variable $link or $con, or whatever you want.

Example

Change the connection from :

@mysql_connect($host, $username, $password) or die("Error message...");
@mysql_select_db($db);

or

@mysql_connect($host, $username, $password, $db) or die("Error message...");

to:

$con = mysqli_connect($host, $username, $password, $db) or die("Error message...");

2. mysql_* modification

With Notepad++ I use "Find in files" (Ctrl + Shift + f) :

in the following order I choose "Replace in Files" :

1. mysql_query( -> mysqli_query($con,

2. mysql_error() -> mysqli_error($con)

3. mysql_close() -> mysqli_close($con)

4. mysql_insert_id() -> mysqli_insert_id($con)

5. mysql_real_escape_string( -> mysqli_real_escape_string($con,

6. mysql_ -> mysqli_

3. adjustments

if you get errors it is maybe because your $con is not accessible from your functions.

You need to add a global $con; in all your functions, for example :

function my_function(...) {
    global $con;
    ...
}

In SQL class, you will put connection to $this->con instead of $con. and replace it in each functions call (for example : mysqli_query($con, $query);)

Answer 2

The easiest way i always handle this Where

 $con = mysqli_connect($serverName,$dbusername,$dbpassword);

3 steps replacement in the following order

1. All "mysql_select_db(" with "mysqli_select_db($con,"
2. All "mysql_query(" with "mysqli_query($con," and
3. All "mysql_" with "mysqli_".

This works for me everytime

Answer 3

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 MySQLi Extension Function Summary is definitely something that will prove helpful.

For instance:

• mysql_connect will be replaced by mysqli_connect
• mysql_error will be replaced by mysqli_error and/or mysqli_connect_error, depending on the context
• mysql_query will be replaced by mysqli_query
• and so on

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 ;-)

Answer 4

If you have a lot files to change in your projects you can create functions with the same names like mysql functions, and in the functions make the convert like this code:

$sql_host =     "your host";      
$sql_username = "username";    
$sql_password = "password";       
$sql_database = "database";       



$mysqli = new mysqli($sql_host , $sql_username , $sql_password , $sql_database );


/* check connection */
if ($mysqli->connect_errno) {
    printf("Connect failed: %s\n", $mysqli->connect_error);
    exit();
}


function mysql_query($query){
    $result = $mysqli->query($query);
    return $result;

}

function mysql_fetch_array($result){
    if($result){
        $row =  $result->fetch_assoc();
         return $row;
       }
}

function mysql_num_rows($result){
    if($result){
         $row_cnt = $result->num_rows;;
         return $row_cnt;
       }
}

Answer 5

In case of big projects, many files to change and also if the previous project version of PHP was 5.6 and the new one is 7.1, you can create a new file sql.php and include it in the header or somewhere you use it all the time and needs sql connection. For example:

//local
$sql_host =     "localhost";      
$sql_username = "root";    
$sql_password = "";       
$sql_database = "db"; 


$mysqli = new mysqli($sql_host , $sql_username , $sql_password , $sql_database );

/* check connection */
if ($mysqli->connect_errno) {
    printf("Connect failed: %s\n", $mysqli->connect_error);
    exit();
}

// /* change character set to utf8 */
if (!$mysqli->set_charset("utf8")) {
    printf("Error loading character set utf8: %s\n", $mysqli->error);
    exit();
} else {
    // printf("Current character set: %s\n", $mysqli->character_set_name());
}
if (!function_exists('mysql_real_escape_string')) {
    function mysql_real_escape_string($string){
        global $mysqli;
        if($string){
            // $mysqli = new mysqli($sql_host , $sql_username , $sql_password , $sql_database );            
            $newString =  $mysqli->real_escape_string($string);
            return $newString;
        }
    }
}
// $mysqli->close();
$conn = null;
if (!function_exists('mysql_query')) {
    function mysql_query($query) {
        global $mysqli;
        // echo "DAAAAA";
        if($query) {
            $result = $mysqli->query($query);
            return $result;
        }
    }
}
else {
    $conn=mysql_connect($sql_host,$sql_username, $sql_password);
    mysql_set_charset("utf8", $conn);
    mysql_select_db($sql_database);
}

if (!function_exists('mysql_fetch_array')) {
    function mysql_fetch_array($result){
        if($result){
            $row =  $result->fetch_assoc();
            return $row;
        }
    }
}

if (!function_exists('mysql_num_rows')) {
    function mysql_num_rows($result){
        if($result){
            $row_cnt = $result->num_rows;;
            return $row_cnt;
        }
    }
}

if (!function_exists('mysql_free_result')) {
    function mysql_free_result($result){
        if($result){
            global $mysqli;
            $result->free();

        }
    }
}

if (!function_exists('mysql_data_seek')) {
    function mysql_data_seek($result, $offset){
        if($result){
            global $mysqli;
            return $result->data_seek($offset);

        }
    }
}

if (!function_exists('mysql_close')) {
    function mysql_close(){
        global $mysqli;
        return $mysqli->close();
    }
}

if (!function_exists('mysql_insert_id')) {
    function mysql_insert_id(){
            global $mysqli;
            $lastInsertId = $mysqli->insert_id;
            return $lastInsertId;
    }
}

if (!function_exists('mysql_error')) {
    function mysql_error(){
        global $mysqli;
        $error = $mysqli->error;
        return $error;
    }
}

Answer 6

I would tentatively recommend using PDO for your SQL access.

Then it is only a case of changing the driver and ensuring the SQL works on the new backend. In theory. Data migration is a different issue.

Abstract database access is great.