php mysql_real_escape_string() function_PHP tutorial

mysql tutorial_real_escape_string() function escapes special characters in strings used in SQL statements.

The following characters are affected:

x00
n
r

'
"
x1a
If successful, the function returns the escaped string. If failed, returns false.

Grammar
mysql_real_escape_string(string,connection) parameter description
string required. Specifies the string to be escaped.
connection is optional. Specifies the MySQL connection. If not specified, the previous connection is used.
Example

function opendatabase ($host,$user,$pass) {
Try {
If ($db = mysql_connect ($host,$user,$pass)){
         return $db;
} else {
          throw new exception ("Sorry, could not connect to mysql.");
}
} catch (exception $e) {
echo $e->getmessage ();
}
}

function selectdb ($whichdb, $db){
Try {
If (!mysql_select_db ($whichdb,$db)){
throw new exception ("Sorry, database could not be opened.");
}
} catch (exception $e) {
echo $e->getmessage();
}
}
function closedatabase ($db){
Mysql_close ($db);
}
$db = opendatabase ("localhost","root","");
selectdb ("mydatabase",$db);
$_POST['user'] = "myname";
$_POST['pass'] = "mypassword";

function validatelogin ($user,$pass){
Mysql_real_escape_string ($user);
Mysql_real_escape_string ($pass);
$thequery = "SELECT * FROM userlogin WHERE username='$user' AND password='$pass'";
If ($aquery = mysql_query ($thequery)){
If (mysql_num_rows ($aquery) > 0){
        return true;
} else {
         return false;
}
} else {
echo mysql_error();
}
}

if (validatelogin ($_POST['user'],$_POST['pass'])){
echo "You have successfully logged in.";
} else {
echo "Sorry, you have an incorrect username and/or password.";
}

closedatabase ($db);

?>

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