Question

Which query is more EXTRA secure?

I have even heard salt(); and md5(); in php5 would been extra secure for mySQL insertion.

$customers_email = mysql_real_escape_string(trim(strtolower($_REQUEST['customers_email'])));    
$customers_email = mysql_real_escape_string(($_REQUEST['customers_email']));

Or even this, I thought of:

$1=$_REQUEST['customers_email'];
$2=$1;
$3=$2;
$4=$3;
$5=$4;
$a=$5;

$xx = mysql_real_escape_string(($a));

My original thread: https://stackoverflow.com/questions/7633993/php-mysql-select-how-to-make-it-secure

Answer 1

None of your queries are more secure than the other. One of them converts the string to all lowercase and trims whitespace. This doesn’t do anything to prevent a SQL injection. Your last query is the same as a plain mysql_real_escape_string($_REQUEST['customers_email']);.