Header does not work

Question

Boa Pessoal,

I have a php file that is named after filling a form in an html file. The function of this php file is to add data to the database and after inserting it has the following code:

if(mysqli_query($con, $sql)){
	echo "<script>
             alert('Inscrição realizada'); //alerta1
     </script>";
      header('Location: ../register.htm');
	}
	else{
		echo "<script>
             alert('Inscrição não realizada'); 
     </script>";
	 header('Location: ../register.htm');
	 }

But after clicking on Submit does not show alert1 nor goes to the page I am telling you to go to. Does anyone know how this is resolved? And someone knows how to go back to the page of form but leave text boxes blank?

Answer 1

Friend, the function header PHP only works when it is placed before any output to the client.

That is, codes like this below will result in error:

<?php

$meus_dados = [1, 2, 3];

foreach($meus_dados as $dado) {
    echo $dado; // saída de dados
}

header('Location: anterior.php'); // Isso resulta em erro pois já houve uma saída

Although not a good practice, if what you need is to redirect after the alert, you can use document.location javascript.

  if (mysqli_query($con, $sql)) {
      echo "<script>
             alert('Inscrição realizada'); //alerta1
             document.location.href = '../register.htm';
           </script>";

    }