PDO和php-在非对象上调用成员函数prepare() [英] PDO and php - Call to a member function prepare() on a non-object
问题描述
我开始学习PDO，但我仍然对PHP初学者有些了解.我正在做一个旨在增加我的知识的项目，但我却遇到了第一个障碍.
出现此错误:在此代码第37行的非对象上调用成员函数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，初始页面在index.php中运行此代码
<?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: " . $bugs->rowCount() . "<br />";
?>
这是将运行find_all_rows函数的页面，该页面上是bugs.class.php文件
<?php
class Bugs {
public function find_all_rows() {
return self::find_by_sql('SELECT * FROM tbl_priority');
}
public function find_by_sql($sql="") {
global $database;
$database->query($sql);
$rows = $database->resultset();
return $rows;
}
}
?>
是否有一个调试工具可以帮助我更好地跟踪这些类型的错误，还是只是对PDO不够熟悉才能发现明显的错误?
@papaja碰到了头上的钉子.您的PDO连接失败，因此您没有PDO对象可以运行prepare方法.
在我的脑海中，我认为您错过了$ dsn字符串的结尾引号.您可能想在$ this-> dbname之后和分号之前添加以下内容:
. "'"
这是用双引号引起来的单引号.我使用以下语法创建DSN字符串:
"mysql:host=$this->HOST;dbname=$this->DATABASE"
无论如何，创建一个测试文件，以便您确切地知道问题所在.测试文件应如下所示:
class TestDatabase{
private $host = DB_HOST;
private $user = DB_USER;
private $pass = DB_PASS;
private $dbname = DB_NAME;
private $dbh;
public function __construct(){
$dsn = 'mysql:host=' . $this->host . ';dbname=' . $this->dbname;
$options = array(
PDO::ATTR_PERSISTENT => true,
PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION
);
$this->dbh = new PDO($dsn, $this->user, $this->pass, $options);
}
}
请注意，我们没有在try catch块中运行PDO对象的实例化.尽管您将永远不会在生产中执行此操作，但这对您的测试很有用，因为它将引发致命的异常，其中包含连接的所有详细信息.
现在实例化测试类，并通过调试收到的错误进行操作.同样，它们将比以前的错误更详细，因为这将是未捕获的PDO异常.
I started learning PDO and im still a bit of a PHP novice. Im doing a project to increase my knowledge but im stuck at the first hurdle.
Im getting this error: Call to a member function prepare() on a non-object on line 37 of this code. This is from 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();
}
}
?>
Now the initial page im running this code in index.php
<?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: " . $bugs->rowCount() . "<br />";
?>
And this is the page it would be running the find_all_rows function on which is the bugs.class.php file
<?php
class Bugs {
public function find_all_rows() {
return self::find_by_sql('SELECT * FROM tbl_priority');
}
public function find_by_sql($sql="") {
global $database;
$database->query($sql);
$rows = $database->resultset();
return $rows;
}
}
?>
Is there a debug tool that will help me trace these type of errors better or is it just a case im not familiar enough with PDO to spot an obvious mistake?
@papaja hit the nail right on the head. Your PDO connection failed, thus you do not have a PDO object to run the prepare method on.
Off the top of my head, I think you are missing the end quote on the $dsn string. You probably want to add the following after $this->dbname and before the semi-colon:
. "'"
That's a single quote wrapped in double quotes. I use the following syntax to create the DSN string:
"mysql:host=$this->HOST;dbname=$this->DATABASE"
Anyway, create a test file so that you know exactly what the problem is. The test file should look like this:
class TestDatabase{
private $host = DB_HOST;
private $user = DB_USER;
private $pass = DB_PASS;
private $dbname = DB_NAME;
private $dbh;
public function __construct(){
$dsn = 'mysql:host=' . $this->host . ';dbname=' . $this->dbname;
$options = array(
PDO::ATTR_PERSISTENT => true,
PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION
);
$this->dbh = new PDO($dsn, $this->user, $this->pass, $options);
}
}
Note that we are not running the instantiation of the PDO object within a try catch block. While you would never ever do that in production, it will be useful for your test because it will throw a fatal exception containing all of the details of your connection.
Now instantiate the test class and proceed by debugging the errors you receive. Again, they will be more detailed than the previous error because it will be an uncaught PDO exception.
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