What is the correct way to make a SELECT in PHP and MYSQL?

How can i do a select from a variable received from a form?

I have the following code but i think that i cannot do this : '%'.$texto.'%'

$busqueda=$_POST['texto'];
$tipo=$_POST['tipo'];

if($tipo='titulo')
    $res=mysql_query("SELECT * FROM LI开发者_如何学GoBRO WHERE LI_TITULO like '%'.$texto.'%'",$conexion);

What should i do? Thank you for your time.

Always do mysql_real_escape_string() on variables or some kind of filtering:

if you expect integer parse the variable

$myId = (int)$POST['id'];

if you expect string with no HTML:

$myString = mysql_real_escape_string(strip_tags($POST['string']));

And so on. Never trust user's input!!!

The best option is to use a PHP framework because all frameworks have thought of potential weaknesses and provide reliable architecture and classes/functions for common tasks, e.g. Database, User login, etc.

Some frameworks you can have a look: CakePHP, CodeIgniter, Zend Framework, Symfony

1. if($tipo == 'titulo'), or you'll always get true there
2. mysql_real_escape_string on any user input that you put in your query strings
3. comment your code

4. indent you SQL, even if it's in a PHP string. like so:

   $res = mysql_query("
       SELECT * 
       FROM `libro` 
       WHERE `li_titulo` LIKE '%".mysql_real_escape_string($texto)."%'
   ", $conexion);
   

5. uppercase only for keywords and maybe functions. MySQL is case insensitive.

mysql_query("SELECT * FROM LIBRO WHERE LI_TITULO like '%{$busqueda}%'",$conexion); 

Edit:

You also have bug in your if statement:

if($tipo='titulo') 

That's not a comparison, it's an assignment. If you want to compare, use

if($tipo==='titulo')