How to Protect from double posting insert MySQL

Submit once even the visitor is refresh the page from browser.
Here is the way to protect.
Use a SESSION.
1. Set a session in the form page

session_start();
$_SESSION[post_only_once] = 1;
echo "
 < form method=\"post\">
  Name < input type=\"text\" name=\"name\">
  < input type=\"submit\" value=\"submit\" name=\"submit\">
 < /form>
";

2. Check the session before doing INSERT into MySQL.

session_start();
if($_SESSION[post_only_once] == 1) {
  // here doing insert to mysql
}
unset($_SESSION[post_only_once]); // remove the session after insert

How to connect MySQL from PHP

$link = mysql_connect('localhost', 'mysql_user', 'mysql_password');
if (!$link) {
    die('Could not connect: ' . mysql_error());
}
echo 'Connected successfully';
mysql_close($link);

PHP Cut string from MySQL

Shorting or cutting the text string from long char into new max lenght.
Here is the code.
PHP CODE

function short_string ($var, $len){    
 if (strlen ($var) < $len) {
  return $var;
 }
 if (preg_match ("/(.{1,$len})\s/", $var, $match)) {
  return $match [1] . "..";
 } else {
  return substr ($var, 0, $len) . ".."; 
 }
}

How to use?
PHPCODE

short_string ("Very very long text is here blablabla", 14);

The Result is:

Very very long..

Insert and Select doing in MySQL from SQL Injection

Here is the save way from RSS Attack SQL Injection.
Get all variable $_POST or $_GET or $_REQUEST or $_SESSION convert into mysql_real_escape string filter, you do not need one by one for all type variable.
here is code.
PHP CODE

$_POST  = array_map('mysql_real_escape_string', $_POST);
$_SESSION  = array_map('mysql_real_escape_string', $_SESSION);
$_COOKIE  = array_map('mysql_real_escape_string', $_COOKIE);

And here is to view back or mysql_unescape_string or mysql_real_unescpae_string or whatever you want to.
PHP CODE

function mysql_real_unescape_string($string){
$string=trim($string);
$string=str_replace("\\","",str_replace("\$","",$string));
   return $string;
}

Convert TEXT2HEX

Here is a php script snippet to convert string text to hex decimal code.
PHP CODE

function text2hex($string) {
 $hex = '';
 $len =
 strlen($string) ;
 for ($i = 0; $i < $len; $i++) {
  $hex .=
  str_pad(dechex(ord($string[$i])), 2, 0, STR_PAD_LEFT);
 }
 return $hex;
}