unset() being executed within a wrong parole

Question

I have an interesting problem: my unset($_SESSION['x']) is running inside an IF that is not true. See my code:

<?php
// Codigo do estado
$cod_estado = $_GET['s'];

// Função da classe Usuario 
$cont_resultado = count(Usuario::CS_GetUsuarios("WHERE cod_estado = " . checarSql($cod_estado)));

// Já tentei < 1, <= 0
if ($cont_resultado == 0) {
    echo "<script>alert('cheguei aqui');</script>"; // So para exemplo
    unset($_SESSION['usuario_estado']);
}
?>

Even if $cont_resultado == 20 he executes the unset() I don’t know why.

Function CS_GetUsuarios():

public function CS_GetUsuarios($sql_aux = false)
{
    global $obj_conexao;
    $str_sql = "SELECT * FROM usuario $sql_aux";

    $vet_dados = $obj_conexao->query($str_sql)->fetchAll();
    return $vet_dados;
}

Suppose I run the following query: SELECT * FROM usuario WHERE cod_estado = 8 and this result returns me in count a value of 20 (a false conditional). It will will not execute the <script>alert</script> but will execute the unset().

Giving a var_dump() before the IF a session exists.

• If IF is true (Count == 0) the session will not exist at the end of the script.
• If IF is false, it will exist at the end of the script.

The whole problem is when I move to some other page of my site, the session is destroyed (even if I have not entered the IF).

The strange thing is that I commented on the line unset($_SESSION['usuario_estado']); and there, the problems are over. The session continues to exist even after I move to other pages.

Complementing: on line 1 of index php. make a include include_once "includes/include.php"; which contains the main functions of my script.

Filing cabinet include.php:

<?php
//error_reporting(E_ALL);
//ini_set( 'display_errors','1');
//ob_start('ob_gzhandler');

// Header
session_start();

// Daqui para baixo só funções
?>

You see, the include.php is present on ALL pages of the script as they are all included through the index php..

What’s wrong with it?

UPDATE: For information purposes only, I was able to solve the problem. My function checarSql() was passing the $cod_estado as string à query, it should be an integer. Thus using Usuario::CS_GetUsuarios("WHERE codEstado = $cod_estado") succeeded.