这是我的代码
class db{
public function connect(){
try{
$db = new PDO("mysql:host=$host; dbname = $dbname", $user , $pass);
return this->$db;
}
catch (PDOException $e){
echo $e->getMessage();
}
}
那么我有另一个类来从数据库中获取一些数据
class getData{
public function getData($table,$where) {
//$where is dynamic and is like array('user'=>$username,'pass'=>$password))
$db = new db();
foreach ($where as $value){
$where_string.=(" AND ".$value."=:".$value);
}
$where_string=substr($where_string,5);
// end up with foo=:foo AND foo=:foo to add in the query
$query_array = array();
foreach ($where as $value){
$query_array[$value]= $value;
}
//end up with array(foo=>foo, foo=>foo); to add in the query
$statement = $db->prepare("select id from table = :table where " .$where_string);
$statement->execute($query_array);
$row = $statement->fetch();
}
}
$where中的getData var未修复，因此我必须循环它并构造查询的where部分和预准备语句的绑定部分。
我总是以Fatal error: Call to undefined method db::prepare() in /home/projectAwesome/public_html/mystuff.php on line 241
我该如何解决这个问题？ PHP应该看到prepare方法，因为它是php的全局模块并且正在运行。 感谢
更新
现在我的代码是
class db extends PDO{
private $host;
private $user;
private $pass;
private $name;
private $link;
private $error;
private $errno;
private $query;
function __construct($myhost='localhost', $myuser='aaa', $mypass='bbb', $myname='ccc', $myconn = 1) {
$this -> host = $myhost;
$this -> user = $myuser;
$this -> pass = $mypass;
if (!empty($myname)) $this -> name = $myname;
if ($myconn == 1) $this -> connect();
}
function __destruct() {
@mysql_close($this->link);
}
public function connect(){
try{
$host = $this -> host;
$dbname = $this -> name;
$user = $this -> user;
$pass = $this -> pass;
$charset = 'utf8';
$dsn = "mysql:host=$host;dbname=$dbname;charset=$charset";
$opt = [
PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
PDO::ATTR_EMULATE_PREPARES => false,
];
$db = new PDO($dsn, $user, $pass, $opt);
return $db;
}
catch (PDOException $e){
echo $e->getMessage();
}
}
}
然后是另一个班级
class getData{
public function getData($table,$where) {
$db = new db();
$where_string = "";
foreach ($where as $key=>$value){
$where_string.=($value."=:".$value." AND ");
}
$where_string=rtrim($where_string, " AND ");
$query_array = array();
foreach ($where as $value){
$query_array[$value]= $value;
}
$statement = $db->prepare("select id from" .$table. "where ".$where_string);
$statement->execute($query_array);
$row = $statement->fetch();
}
}
现在错误
Warning: PDO::prepare(): SQLSTATE[00000]: No error: PDO constructor was not called in /home/... on line 254
Fatal error: Call to a member function execute() on null in /home/... on line 255
请指教。谢谢
答案 0 :(得分：2)
您可能会发现一些疏忽。 1.）db类中的connect（）方法无法访问变量：$ host，$ user，$ pass等.2。）getData类中的getData方法实例化db类而没有任何方法db类获取有关$ host，$ user，$ pass等变量的信息。将这些变量定义为常量可能是理想的，然后您不必一直传递它们。否则，这可以帮到你：
<?php
class db extends PDO{
public function connect($host, $dbname, $user, $pass) {
try {
$db = new PDO("mysql:host=$host;dbname=$dbname", $user, $pass);
return $this->$db;
} catch (PDOException $e) {
echo $e->getMessage();
}
}
}
class getData{
public function getData($table, $where, $host, $dbname, $user, $pass) {
//$where is dynamic and is like array('user'=>$username,'pass'=>$password))
$db = new db($host, $dbname, $user, $pass);
$where_string = "";
foreach ($where as $key=>$value){
$where_string .= ($value."=:".$value . " AND ");
}
// REMOVE SURPLUS " AND " TO THE RIGHT OF THE STRING...
$where_string = rtrim($where_string, " AND ");
// $where_string = substr($where_string,5); //<== WHY substr? WHAT'S YOUR INTENTION HERE?
// end up with foo=:foo AND foo=:foo to add in the query
$query_array = array();
foreach ($where as $value){
$query_array[$value]= $value;
}
//end up with array(foo=>foo, foo=>foo); to add in the query
$statement = $db->prepare("select id from table " . $table . " where " . $where_string);
$statement->execute($query_array);
$row = $statement->fetch();
}
}
更新：DB CLASS
<?php
class db extends PDO{
private $host;
private $user;
private $pass;
private $dbh;
private $name;
private $link;
private $error;
private $errno;
private $query;
function __construct($myhost='localhost', $myuser='aaa', $mypass='bbb', $myname='ccc', $myconn = 1) {
$this -> host = $myhost;
$this -> user = $myuser;
$this -> pass = $mypass;
if (!empty($myname)){
$this->name = $myname;
}
if ($myconn == 1){
if(isset($this->dbh)){
return $this->dbh;
}
return $this->connect();
}
}
function __destruct() {
$this->dbh = null;
}
public function connect(){
try{
$host = $this -> host;
$dbname = $this -> name;
$user = $this -> user;
$pass = $this -> pass;
$charset = 'utf8';
$dsn = "mysql:host=$host;dbname=$dbname;charset=$charset";
$opt = [
PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
PDO::ATTR_EMULATE_PREPARES => false,
];
$this->dbh = new PDO($dsn, $user, $pass, $opt);
return $this->dbh ;
}
catch (PDOException $e){
echo $e->getMessage();
}
}
}