paad/action/action_materias_select.php

<?php
    $ruta = "../";
    require_once "../include/bd_pdo.php";
    global $pdo;
    $sql="SELECT * FROM materia WHERE materia_id = :idMateria";
    $params = ['idMateria' => $_POST['idmateria']];
    echo json_encode(query($sql, $params, false));
?>