<?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;
}
?>

mysql_query($query)

mysqli_query($link, $query)

//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: %sn", $mysqli->connect_error);
    exit();
}

// /* change character set to utf8 */
if (!$mysqli->set_charset("utf8")) {
    printf("Error loading character set utf8: %sn", $mysqli->error);
    exit();
} else {
    // printf("Current character set: %sn", $mysqli->character_set_name());
}
if (!function_exists('mysql_real_escape_string')) {
    function mysql_real_escape_string($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;
    }
}

$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: %sn", $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;
       }
}

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

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

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

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

mysql_connect ---> mysqli_connect
mysql_select_db  ---> mysqli_select_db
mysql_error ---> mysqli_connect_error()
mysql_query ---> mysqli_query
mysql_fetch_assoc  ---> mysqli_fetch_assoc

$conn = mysqli_connect($db_host, $db_username, $db_password, $db_name) or die("Unable to Connect");