Php mysqli_query（）要求参数1为mysqli，如果给定空值：(

当我运行代码时，它会显示此错误。“mysqli_query（）期望参数1为mysqli，给定null”

---

如果这是您的完整文件，则

$connection

将为空（null），您不会在任何地方创建连接

---

您可能正在另一个文件中创建连接，因此，

global$connection；

但是您需要包含此文件才能获得连接。

您正在混合使用

mysql\uu

和

mysqli

函数。这可能是您的问题。您不能在代码中混合使用mysqli和mysql函数。

试试这个。

$link = mysqli_connect("localhost", "my_user", "my_password", "world");

/* check connection */
if (mysqli_connect_errno()) {
    printf("Connect failed: %s\n", mysqli_connect_error());
    exit();
}

/* Create table doesn't return a resultset */
if (mysqli_query($link, "CREATE TEMPORARY TABLE myCity LIKE City") === TRUE) {
    printf("Table myCity successfully created.\n");
}

/* Select queries return a resultset */
if ($result = mysqli_query($link, "SELECT Name FROM City LIMIT 10")) {
    printf("Select returned %d rows.\n", mysqli_num_rows($result));

    /* free result set */
    mysqli_free_result($result);
}

仅从php.net获得此信息

我的数据库连接是mysqli:（…这是代码

$link = mysqli_connect("localhost", "my_user", "my_password", "world");

/* check connection */
if (mysqli_connect_errno()) {
    printf("Connect failed: %s\n", mysqli_connect_error());
    exit();
}

/* Create table doesn't return a resultset */
if (mysqli_query($link, "CREATE TEMPORARY TABLE myCity LIKE City") === TRUE) {
    printf("Table myCity successfully created.\n");
}

/* Select queries return a resultset */
if ($result = mysqli_query($link, "SELECT Name FROM City LIMIT 10")) {
    printf("Select returned %d rows.\n", mysqli_num_rows($result));

    /* free result set */
    mysqli_free_result($result);
}