All Questions

Reviewing the configuration CodeIgniterI came across the following line:

$config['permitted_uri_chars'] = 'a-z 0-9~%.:_\-';

And the documentation for it says:

/*
|--------------------------------------------------------------------------
| Allowed URL Characters
|--------------------------------------------------------------------------
|
| This lets you specify which characters are permitted within your URLs.
| When someone tries to submit a URL with disallowed characters they will
| get a warning message.
|
| As a security measure you are STRONGLY encouraged to restrict URLs to
| as few characters as possible.  By default only these are allowed: a-z 0-9~%.:_-
|
| Leave blank to allow all characters -- but only if you are insane.
|
| The configured value is actually a regular expression character group
| and it will be executed as: ! preg_match('/^[<permitted_uri_chars>]+$/i
|
| DO NOT CHANGE THIS UNLESS YOU FULLY UNDERSTAND THE REPERCUSSIONS!!
|
*/

/*
|--------------------------------------------------------------------------
| Caracteres URL permitidos
|----------------------------------------------------------------------
|
|Esto permite especificar qué caracteres están permitidas dentro de sus URL. 
|Cuando alguien trata de enviar una URL con caracteres no permitidos se les 
|dará un mensaje de advertencia.
|
|Como medida de seguridad, se recomienda enfáticamente restringir las direcciones 
|URL a la menor cantidad de caracteres posible. 
|Por defecto sólo se permiten éstos: a-z ~ 0-9%:. _-
|
|Dejar en blanco para permitir todos los caracteres -- pero sólo si estás loco.
|
|El valor configurado es actualmente una expresión regular de agrupamiento 
|de caracteres y sera ejecutada como: ! preg_match('/^[<permitted_uri_chars>]+$/i
|
|NO CAMBIES ESTO HASTA QUE COMPRENDAS COMPLETAMENTE LAS REPERCUSIONES!!
|
*/

However, it is not entirely clear to me what repercussions or security problems may arise from allowing all characters in a url.

Regardless of the language used, what problems can this situation generate?

This is an example of my doubt, why put "this" at the beginning instead of just putting "wheels = 4" or "seats = 1", etc. How can this help me when programming?

var Car = function() {
  this.wheels = 4;
  this.seats = 1;
  this.engines = 1;
};

Good afternoon people!. I have searched for half an hour and I have not found anything that works for me or gives me positive results. I have a pivot table that changes the number of rows to display based on what one selects from the DropDownList. The problem is that for those cases in which the table has few rows, the footer gets out of place and, as you can see below, it is not "stuck" properly to the footer.

I have tried with the position attribute, with others of which I had never heard but I can't get the footer to always stick to the footer. At the moment this is what I have in my css;

footer
{
    margin-top:50px;
    width:100%;
    height:200px;
    background-color:red;
}

From already thank you very much!

Normally I do iterations using the control statement forand thus I get the index of the iteration easily, but the question I have is the following, Is there a way to get the index of the iteration in an foreachen c#?

since I usually get it out like this:

int i=0;
foreach (var item in array)
{

   i++;
}

The other question would be, if there is a way to get the index in a different way than the example, what is it?

Reviewing JavaScript code, I saw these two types of functions:

function EjemploUno(){
   //código
}

var EjemploDos = function(){
   //código
}

So, what is the difference between one and the other? When should you use one or the other?