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; } ?> 

Answer 1

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 2

(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.