echo函数未显示任何输出

Question

<?php
session_start();

if (isset($_POST["user_name"]) && isset($_POST["user_pwd"])) {
    include"php/connect_to_mysql.php";
    $user_name = preg_replace('#[^A-Za-z0-9]#i', '', $_POST["user_name"]);
    $user_pwd = preg_replace('#[^A-Za-z0-9]#i', '', $_POST["user_pwd"]);

    $sql = "SELECT * FROM user_ac WHERE user='$user_name' OR email='$user_name' AND pwd='$user_pwd' LIMIT 1";
    $result = mysqli_query($myConnection, $sql);

    if (mysqli_num_rows($result) > 0) {
        echo "Successfully Logged In";
        header("location: login.html?abc=234");
    } else {

    }
} else {

}    

In this code, inside the second if statement, echo is not displaying anything, but the header function executes correctly.

Please help, thanks.

Answer 1

You cannot see the echo because you are going to another page.

As test, remove the header("location: login.html?abc=234"); and you will see the echo.