早上好。
我正在尝试创建一个DB类来连接我的DB并从中检索结果。所以，我认为有课就是一切都好。但是，结果不会出现。
这是我的DB类：
<?php class Conexao {
var $host = "localhost";
var $usuario = "root";
var $senha = "xxxxxx";
var $banco = 'restaurante';
private $mysqli;
public function Abrir()
{
$this->mysqli = new mysqli($this->host, $this->usuario, $this->senha, $this->banco);
}
public function Fechar()
{
$this->mysqli->close();
}
}
class Comando {
public function Executar($sql)
{
$con = new Conexao();
$con->Abrir();
$re = $con->mysqli->query($sql);
$con->Fechar();
return $re;
}
}
?>
这里是我试图检索结果的地方：
<?php
$queryMesasAtivas = Comando::Executar('SELECT * FROM mesas WHERE status =1 AND numero !="'.$_SESSION["mesa"].'"');
if ($queryMesasAtivas->num_rows > 0) {
while ($rowMesasAtivas = $queryMesasAtivas->fetch_assoc()) {
echo "<option value='".$rowMesasAtivas['numero']."'>Mesa ".$rowMesasAtivas['numero']."</option>";
}
}
else {
echo '<option>Nenhuma mesa ativa</option>';
}
?>
我尝试了一些修改，但没有什么变化。每次它仍然不起作用。怎么了？
由于Comando::Executar不是静态的，而是声明为public function...，因此必须执行以下操作：
$comando = new Comando();
$queryMesasAtivas = $comando->Executar('SELECT * FROM mesas WHERE status =1 AND numero !="'.$_SESSION["mesa"].'"');
if ($queryMesasAtivas->num_rows > 0) {
while ($rowMesasAtivas = $queryMesasAtivas->fetch_assoc()) {
echo "<option value='".$rowMesasAtivas['numero']."'>Mesa ".$rowMesasAtivas['numero']."</option>";
}
}
else {
echo '<option>Nenhuma mesa ativa</option>';
}
或者将方法声明为静态，即：
public static function Executar($sql)
{
$con = new Conexao();
$con->Abrir();
$re = $con->mysqli->query($sql);
$con->Fechar();
return $re;
}
然后您可以使用双冒号（::）语法：
$queryMesasAtivas = Comando::Executar('SELECT * FROM mesas WHERE status =1 AND numero !="'.$_SESSION["mesa"].'"');
我建议不要每次运行查询时都调用open和close，而应该调用这样的类：
class Conexao
{
private $link;
public function __construct($host = null, $username = null, $password = null, $dbName = null)
{
$this->link = mysqli_init();
$this->link->real_connect($host, $username, $password, $dbName) or die("Failed to connect");
}
public function __destruct()
{
$this->link->close();
}
public function Query($sql)
{
return $this->link->query($sql);
}
}
然后这样使用：
$conexao = new Conexao("host", "username", "password", "db_name");
$result = $conexao->Query("SELECT * FROM `table` WHERE 1 ORDER BY `id` ASC;");
这不仅更小，而且在服务器上更轻，因为您不会永久打开和关闭数据库连接，从而减少CPU使用和内存使用。
为主机等使用静态属性（即使在使用__destruct之后也将它们保存在内存中，因此不需要每次都重新声明它们）：
class Conexao
{
private $link;
private static $host, $username, $password, $dbName;
public function __construct($host = null, $username = null, $password = null, $dbName = null)
{
static::$host = $host ? $host : static::$host;
static::$username = $username ? $username : static::$username;
static::$password = $password ? $password : sattic::$password;
static::$dbName = $dbName : $dbName : static::$dbName;
$this->link = mysqli_init();
$this->link->real_connect(static::$host, static::$username, static::$password, static::$dbName) or die("Failed to connect");
}
public function __destruct()
{
$this->link->close();
}
public function Query($sql)
{
return $this->link->query($sql);
}
}
$conexao = new Conexao("host", "username", "password", "db_name");
$result = $conexao->Query("SELECT * FROM `table` WHERE 1 ORDER BY `id` ASC;");
$conexao->__destruct(); // Destroy the class
$conexao = new Conexao(); // Reinitialise it
$result = $conexao->Query("SELECT * FROM `table` WHERE 1 ORDER BY `id` ASC;");
使用连接类的配置实例：
config.php文件：
<?php
require_once 'path/to/Conexao.php';
$conexao = new Conexao("host", "username", "password", "db_name");
?>
index.php文件：
<?php
require_once 'config.php';
$result = $conexao->Query("SELECT * FROM `table` WHERE 1 ORDER BY `id` ASC;");
?>
该类现在在我的github上有一个家长！