我开始学习 PDO，但我还是个 PHP 新手。我正在做一个项目来增加我的知识，但我陷入了第一个障碍。
我收到此错误：在此代码的第 37 行调用非对象上的成员函数 prepare()。这是来自 database.class.php
<?php
// Include database class
include 'config.php';
class Database{
private $host = DB_HOST;
private $user = DB_USER;
private $pass = DB_PASS;
private $dbname = DB_NAME;
private $dbh;
private $error;
public function __construct(){
// Set DSN
$dsn = 'mysql:host=' . $this->host . ';dbname=' . $this->dbname;
// Set options
$options = array(
PDO::ATTR_PERSISTENT => true,
PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION
);
// Create a new PDO instanace
try{
$this->dbh = new PDO($dsn, $this->user, $this->pass, $options);
}
// Catch any errors
catch(PDOException $e){
$this->error = $e->getMessage();
}
}
// this variable holds the temporary statement
private $stmt;
// prepare our values to avoid SQL injection
public function query($query){
$this->stmt = $this->dbh->prepare($query);
}
// use switch to select the appropiate type for the value been passed
// $param = placeholder name e.g username, $value = myusername
public function bind($param, $value, $type = null){
if (is_null($type)) {
switch (true) {
case is_int($value):
$type = PDO::PARAM_INT;
break;
case is_bool($value):
$type = PDO::PARAM_BOOL;
break;
case is_null($value):
$type = PDO::PARAM_NULL;
break;
default:
$type = PDO::PARAM_STR;
}
}
// run the binding process
$this->stmt->bindValue($param, $value, $type);
}
// execute the prepared statement
public function execute(){
return $this->stmt->execute();
}
// returns an array of the results, first we execute and then fetch the results
public function resultset(){
$this->execute();
return $this->stmt->fetchAll(PDO::FETCH_ASSOC);
}
// same as resultset() except this returns a single result
public function result_single(){
$this->execute();
return $this->stmt->fetch(PDO::FETCH_ASSOC);
}
// count the number of rows from the previous delete, update or insert statement
public function rowCount(){
return $this->stmt->rowCount();
}
// last insert id return the last id of the insert made, useful if you need to run a further
// query on the row you just inserted and need the id as the reference
public function lastInsertId(){
return $this->dbh->lastInsertId();
}
// transactions allow you to rollback if a set of queries fail but it also allows ensures
// we avoid errors due to users interaction while half of the queries are still being written
// the following code begins a transaction
public function beginTransaction(){
return $this->dbh->beginTransaction();
}
// end a transaction
public function endTransaction(){
return $this->dbh->commit();
}
// rollback a transaction
public function cancelTransaction(){
return $this->dbh->rollBack();
}
// this dumps the PDO information from the prepared statement for debug purposes
public function debugDumpParams(){
return $this->stmt->debugDumpParams();
}
}
?>
现在，我在 index.php 中运行此代码的初始页面
<?php
// Include database connection class
include 'includes/database.class.php';
include 'includes/bug.class.php';
$database = new Database;
$bugs = new Bugs;
$bugs->find_all_rows();
echo "<pre>";
print_r($rows);
echo "</pre>";
echo "Number of rows: " . $bugs->rowCount() . "<br />";
?>
这是它将运行 find_all_rows 函数的页面，在该页面上是 bugs.class.php 文件
<?php
class Bugs {
public function find_all_rows() {
return self::find_by_sql('SELECT * FROM tbl_priority');
}
public function find_by_sql($sql="") {
global $database;
$database->query($sql);
$rows = $database->resultset();
return $rows;
}
}
?>
是否有调试工具可以帮助我更好地跟踪这些类型的错误，或者只是我对 PDO 不够熟悉而无法发现明显错误的情况？