php mysqli_select_db() 期望参数 1 是 mysqli，给定的字符串
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mysqli_select_db() expects parameter 1 to be mysqli, string given
提问by user1551909
I am new to Mysqli_* and I am getting these errors:
我是 Mysqli_* 的新手，出现以下错误：
Warning: mysqli_select_db() expects parameter 1 to be mysqli, string given in D:\Hosting\9864230\html\includes\connection.php on line 11
Warning: mysqli_error() expects exactly 1 parameter, 0 given in D:\Hosting\9864230\html\includes\connection.php on line 13
警告：mysqli_select_db() 期望参数 1 为 mysqli，字符串在 D:\Hosting\9864230\html\includes\connection.php 中第 11 行
警告：mysqli_error() 需要 1 个参数，0 在第 13 行的 D:\Hosting\9864230\html\includes\connection.php 中给出
Database selection failed:
数据库选择失败：
<?php
require("constants.php");
// 1. Create a database connection
$connection = mysqli_connect(DB_SERVER,DB_USER,DB_PASS);
if (!$connection) {
die("Database connection failed: " . mysqli_error());
}
// 2. Select a database to use
$db_select = mysqli_select_db(DB_NAME,$connection);
if (!$db_select) {
die("Database selection failed: " . mysqli_error());
}
?>
回答by Chris McKnight
Your arguments are in the wrong order. The connection comes first according to the docs
你的论点顺序错误。根据文档，连接首先出现
<?php
require("constants.php");
// 1. Create a database connection
$connection = mysqli_connect(DB_SERVER,DB_USER,DB_PASS);
if (!$connection) {
error_log("Failed to connect to MySQL: " . mysqli_error($connection));
die('Internal server error');
}
// 2. Select a database to use
$db_select = mysqli_select_db($connection, DB_NAME);
if (!$db_select) {
error_log("Database selection failed: " . mysqli_error($connection));
die('Internal server error');
}
?>
回答by Barmar
// 2. Select a database to use
$db_select = mysqli_select_db($connection, DB_NAME);
if (!$db_select) {
die("Database selection failed: " . mysqli_error($connection));
}
You got the order of the arguments to mysqli_select_db()backwards. And mysqli_error()requires you to provide a connection argument. mysqli_XXX is not like mysql_XXX, these arguments are no longer optional.
你得到了mysqli_select_db()向后的参数顺序。并mysqli_error()要求您提供连接参数。mysqli_XXX 不像 mysql_XXX，这些参数不再是可选的。
Note also that with mysqli you can specify the DB in mysqli_connect():
另请注意，使用 mysqli 您可以在mysqli_connect()以下位置指定数据库：
$connection = mysqli_connect(DB_SERVER, DB_USER, DB_PASS, DB_NAME);
if (!$connection) {
die("Database connection failed: " . mysqli_connect_error();
}
You mustuse mysqli_connect_error(), not mysqli_error(), to get the error from mysqli_connect(), since the latter requires you to supply a valid connection.
您必须使用mysqli_connect_error()，而不是mysqli_error()从 获取错误mysqli_connect()，因为后者要求您提供有效的连接。
