Change XML numbers using PHP file with form

Question

The following PHP code performs a click search and displays all required XML data, however, even with the PHP script to increase and decrease XML values in 1, when clicking on + or -, it just returns the main page(e.php) without having effected the change.

How can I make such changes within the form below so that an initial limit equal to 0 and a final limit equal to media_total?

PHP file: e.php

<meta charset="UTF-8">
<style type="text/css">body{background-color: rgba(25,25,25,1); color: rgba(255,255,255,0.5);}</style>
<form action="e.php" method="post"><input type="hidden" name="status" value="Acompanhando"/><input type="submit" name="submit" value="Acompanhando"/></form>
<?php
if(isset($_POST['submit'])){
    $string = file_get_contents("minha_lista.xml");
    $xml = simplexml_load_string($string);
    $erro = 0;
    $i = 1;
    echo "<center>";
    foreach($xml->lista AS $val){
        if($val->status==$_POST['status']){
            $titulo = $val->titulo;
            $media_acompanhada = $val->media_acompanhada;
            $valor_da_media_acompanhada_positiva = 1;
            $valor_da_media_acompanhada_negativa = 1;
            echo "o Título é <code style='color: rgba(255,130,0,1);'>".$titulo."</code> e a Média acompanhada é <code style='color: rgba(0,255,255,1);'>".$media_acompanhada."</code>";
        ?>
        <form action="" method="post">
            <label><button hidden name="media_acompanhada[<?php echo $valor_da_media_acompanhada_positiva++; ?>]" value="<?php echo $media_acompanhada+1; ?>"></button>+</label>
            <div class="mudanca_de_cursor" style="display: inline;">/</div>
            <label><button hidden name="media_acompanhada[<?php echo $valor_da_media_acompanhada_negativa++; ?>]" value="<?php echo $media_acompanhada-1; ?>"></button>-</label>
        </form>
        <?php
            if (isset($_POST['media_acompanhada'])){
                $medias_acompanhadas = (array) $_POST['media_acompanhada'];
                $carregador_xml = simplexml_load_file('minha_lista.xml');
                $funcao = fopen("minha_lista.xml", "wb");
                foreach ($medias_acompanhadas as $num => $media_acompanhada){
                    $valor_da_media_acompanhada = 1;
                    foreach ($carregador_xml->children() as $lista){
                        if ($valor_da_media_acompanhada++ == $num ){
                            $lista->media_acompanhada = $media_acompanhada;
                            break 1;
                        }
                    }
                }
                fwrite($funcao, $carregador_xml->asXML());
                fclose($funcao);
                echo '<script type="text/javascript">window.location.href=window.location.href;</script>';
            }
        ?>
        <?php
            $erro++;
        }
    }
    if($erro == 0){
        echo "Nenhum valor encontrado";
    }
    echo "</center>";
}
?>

XML file: minha_lista.xml

<?xml version="1.0" encoding="UTF-8"?>
<banco_de_dados>
    <lista>
        <titulo>A</titulo>
        <media_acompanhada>6</media_acompanhada>
        <media_total>8000</media_total>
        <status>Acompanhando</status>
    </lista>
    <lista>
        <titulo>C</titulo>
        <media_acompanhada>10</media_acompanhada>
        <media_total>40000</media_total>
        <status>Acompanhando</status>
    </lista>
</banco_de_dados>