SQL injection

<?php

function input( $string ) {

	$string = mysql_real_escape_string( $string );
	
	return $string;

}

function output( $string ){

	$string = htmlspecialchars( $string );
	$string = stripslashes( $string );

	return $string;

}

?>

<?php
 
function input( $string ) {
 
	$string = mysql_real_escape_string( $string );
 
	return $string;
 
}
 
function output( $string ){
 
	$string = htmlspecialchars( $string );
	$string = stripslashes( $string );
 
	return $string;
 
}
 
?>

<?php
if (!empty($_POST['submit'])) //als het formulier verzonden wordt
{
	//klein scriptje tegen injection (altijd boven je query)
	if (get_magic_quotes_gpc())
	{
	    foreach ($_POST as $k => $v)
	    {
	        $_POST[$k] = stripslashes($v);
	    }
	}

	foreach ($_POST as $k => $v)
	{
	    if(version_compare(phpversion(),"4.3.0") == "-1")
	    {
	        $_POST[$k] = mysql_escape_string($v);
	    }
	    else
	    {
	        $_POST[$k] = mysql_real_escape_string($v);
	    }
	}

	//MySQL query
	mysql_query("INSERT INTO tabel (id, test, blaat) VALUES ('', '".$_POST['test']."', '".$_POST['blaat']."')");
}
else
{
	//formulier
}
?>

<?php
if (!empty($_POST['submit'])) //als het formulier verzonden wordt
{
	//klein scriptje tegen injection (altijd boven je query)
	if (get_magic_quotes_gpc())
	{
	    foreach ($_POST as $k => $v)
	    {
	        $_POST[$k] = stripslashes($v);
	    }
	}
 
	foreach ($_POST as $k => $v)
	{
	    if(version_compare(phpversion(),"4.3.0") == "-1")
	    {
	        $_POST[$k] = mysql_escape_string($v);
	    }
	    else
	    {
	        $_POST[$k] = mysql_real_escape_string($v);
	    }
	}
 
	//MySQL query
	mysql_query("INSERT INTO tabel (id, test, blaat) VALUES ('', '".$_POST['test']."', '".$_POST['blaat']."')");
}
else
{
	//formulier
}
?>

<?php
if (is_numeric($_GET['id']))
{
	//MySQL query
	$query = mysql_query("SELECT * FROM tabel WHERE id='".$_GET['id']."'");
}
else
{
	//fout
}
?>

<?php
if (is_numeric($_GET['id']))
{
	//MySQL query
	$query = mysql_query("SELECT * FROM tabel WHERE id='".$_GET['id']."'");
}
else
{
	//fout
}
?>

<?php

function input( $string ) {

  return mysql_real_escape_string( $string );

}

function output( $string ){

  return htmlspecialchars( stripslashes( $string ) );

}

<?php
 
function input( $string ) {
 
  return mysql_real_escape_string( $string );
 
}
 
function output( $string ){
 
  return htmlspecialchars( stripslashes( $string ) );
 
}