PHP - Moodle - Error de sufijo en html

<?php

   if ($_GET["errorcode"] == 3){

      echo '<scrip>alert("Las credenciales introducidas son inválidas");</script>';

   }

?>

<?php

   if (optional_param('errorcode', 0, PARAM_INT) == 3) {

      echo '<scrip>alert("Las credenciales introducidas son inválidas");</script>';

   }

?>

<form action="https://midominio.com/moodle/login/index.php" id="login" method="POST" >

<input class="input" id="username" name="username" type="text" placeholder="Usuario"

value="" required />

<input class="input" id="password" name="password" type="password" placeholder="Contraseña" value="" required />

	</p>

		<button  style="background-color: transparent" id="contraseña" class=" " type="button" onclick="mostrarContrasena()"><i class="fa fa-eye-slash"></i></button>

		<font color="#000000"><input id= "entrar" name="submit" nbsp="nbsp" type="submit"  onclick="entrar()" value="Entrar"/>

		</form>

if ( isset($_REQUEST['errorcode']) and $_REQUEST['errorcode']==3 )

if ( isset($_GET['errorcode']) and $_GET['errorcode']==3 )

<form action="https://inebchamil.edu.gt/moodle-copia/login/index.php" id="login" method="POST" >

<input class="input" id="username" name="username" type="text" placeholder="Usuario"

value="" required />

<input class="input" id="password" name="password" type="password" placeholder="Contraseña" value="" required />

	</p>

		<button  style="background-color: transparent" id="contraseña" class=" " type="button" onclick="mostrarContrasena()"><i class="fa fa-eye-slash"></i></button>

		<font color="#000000"><input id= "entrar" name="submit" nbsp="nbsp" type="submit"  onclick="entrar()" value="Entrar"/>

		</form>

              </div>

            </div>

            </div>

        </div>

					</div>

<?php

if ( isset($_REQUEST['errorcode']) and $_REQUEST['errorcode']==3 )

{

echo '<scrip>alert("Las credenciales introducidas son inválidas");</script>';

}

?>

echo '<script>alert("Las credenciales introducidas son inválidas");</script>';

// Cuidado que tienes <scrip>!!!

<form action="https://inebchamil.edu.gt/moodle-copia/login/index.php" id="login" method="POST" >

<input class="input" id="username" name="username" type="text" placeholder="Usuario"

value="" required />

<input class="input" id="password" name="password" type="password" placeholder="Contraseña" value="" required />

	</p>

		<button  style="background-color: transparent" id="contraseña" class=" " type="button" onclick="mostrarContrasena()"><i class="fa fa-eye-slash"></i></button>

		<font color="#000000"><input id= "entrar" name="submit" nbsp="nbsp" type="submit"  onclick="entrar()" value="Entrar"/>

		</form>

              </div>

            </div>

            </div>

        </div>

					</div>

<?php

if ( isset($_REQUEST['errorcode']) and $_REQUEST['errorcode']==3 )

{

echo "<script>alert("Las credenciales introducidas son inválidas");</script>";

?>

(PROBÉ CON LAS COMILLAS Y LA COMILLA SIMPLE)

}

<?php

if ( isset($_REQUEST['errorcode']) and $_REQUEST['errorcode']==3 )

{

echo '<script>alert("Las credenciales introducidas son inválidas");</script>';

}

?>

echo '<script>alert("Las credenciales introducidas son inválidas");</script>';

<?php

   if (optional_param('errorcode', 0, PARAM_INT) == 3) {

      echo 'Las credenciales introducidas son inválidas';

   }

?>

var_dump(optional_param('errorcode', 0, PARAM_INT) == 3);

var_dump(optional_param('errorcode', 0, PARAM_INT) == 3);