cannot modify header information

[brsastre]

Hi. I am relatively new to PHP.

I'm trying to make a user authentication, and sending the user to another page if succeeded, with the following code:

 

<?php

include ('../conexion.php');

 

$nombreUsuario = $_POST['nombreusuario'];

$password = $_POST['password'];

 

var_dump($nombreUsuario);

var_dump($password);

 

$consultaAdmin= "SELECT * FROM usuarios WHERE nombre_usuario = '$nombreUsuario' AND password = '$password' AND tipo = 'admin'";

$resultadoAdmin = mysqli_query($conn , $consultaAdmin);

$cantidad= mysqli_num_rows($resultadoAdmin);

 

if($cantidad==1) {

header("location:listado_recetas.php?bienvenida=si");

}else {

header("location:index.php?error=si");

}

?>

 

I am getting this error: 

 

string( "brsastre" string(10) "igor123123" 

Warning: Cannot modify header information - headers already sent by (output started at /Applications/MAMP/htdocs/recetario/admin/validar.php:7)...

 

If I remove var_dump's it works just fine.

 

Why is this happening?

[NotionCommotion]

Once you echo anything, you cannot set any headers or sessions.  Do all your work first, and then display content.  Even a simple empty space is too much.

 

PS.  You are not escaping your SQL.  Recommend using prepared statements all the time until you know when you can do differently

[mikesta707]

Try removing/commenting out the vardumps. As Notion said, you can't send headers after you have output something to the page. Also make sure there isn't even a space before your PHP tags, or any HTML tags above it. 

 

Those vardumps look like the culprits though.