PDO Basics Tutorial in PHP Entry Level_PHP Tutorial

PDO is a major new feature added to PHP 5, because before PHP 5, php4/php3 had a bunch of database extensions to connect and process each database, such as php_mysql.dll, php_pgsql.dll, php_mssql.dll, php_sqlite .dll and other extensions to connect to MySQL, PostgreSQL, MS SQL Server, SQLite. Similarly, we must use database abstract classes such as ADOdb, PEAR::DB, PHPlib::DB to help us, which is extremely cumbersome and inefficient. After all, how can the efficiency of PHP code be so high that we write it directly in C/C++? Therefore, the emergence of PDO is inevitable. Everyone should accept its use with a calm learning attitude. Maybe you will find that it can save you a lot of effort.

Installing PDO
I am on Windows XP SP2, so the whole process is carried out on Windows. As for Linux/FreeBSD and other platforms, please find the information and set up the installation by yourself.
Mine is PHP 5.1.4, which already comes with the php_pdo.dll extension, but it requires a little setup before it can be used.
Open c:windowsphp.ini, which is my PHP configuration file, and find the following line:
extension_dir

This is the directory where our extension exists. My PHP 5 extension is in: C :php5ext, then I will change this line to:

Copy code The code is as follows:

extension_dir = "C:/ php5/ext"

Then go to php.ini and find:

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; Dynamic Extensions ;


There are a bunch of things like; extension=php_mbstring.dll below. Here is the configuration for PHP extension loading. We will add our PDO at the end. Extensions:
extension=php_pdo.dll
extension=php_pdo_mysql.dll
extension=php_pdo_pgsql.dll
extension=php_pdo_sqlite.dll
extension=php_pdo_mssql.dll
extension=php_pdo_odbc. dll
extension=php_pdo_firebird.dll
;extension=php_pdo_oci8.dll

All PDO drivers can be added, but the following php_pdo_oci8.dll, Because I did not install the Oralce database, I did not have this, so I used a semicolon to comment it out. Then restart our web server, IIS/Apache, mine is IIS, hey, you look down on me, on Windows, it’s easy. After restarting, write a phpinfo.php file in the document directory of our web server and add these:

Copy the code The code is as follows:

　phpinfo();
?>

In the output content, if you can see it smoothly:
PDO
PDO support enabled
PDO drivers mysql, pgsql, sqlite, mssql, odbc, firebird
There are various driver descriptions at the back: PDO_Firebird, pdo_mssql, pdo_mysql, PDO_ODBC, pdo_pgsql, pdo_sqlite. Well, congratulations on your successful installation, otherwise please check the above steps carefully.

PDO Tutorial

I am using MySQL 4.0.26, but I personally recommend you to use MySQL 4.1.x or MySQL 5.0.x, because those versions have a lot of interesting things worth learning. . What our PDO needs to connect to is my MySQL 4.0. If you have not installed MySQL, please install it yourself. We have established MySQL and added table foo to the test library, including four fields such as id, name, gender, and time.

We start to construct the first PDO application and create a pdo.php file in the Web document directory:

Copy the code The code is as follows:

　$dsn = "mysql:host=localhost;dbname=test";
　$db = new PDO($dsn, 'root', '') ;
　$count = $db->exec("INSERT INTO foo SET name = 'heiyeluren',gender='male',time=NOW()");
echo $count;
$ db = null;
?>

$dsn = "mysql:host=localhost;dbname=test";

is to construct our DSN (data source) and look at the information inside: the database type is mysql, and the host address is localhost , the database name is test, just a few pieces of information. The data source construction methods of different databases are different.
$db = new PDO($dsn, 'root', '');

Initialize a PDO object. The first parameter of the constructor is our data source, and the second parameter is to connect to the database. The user of the server, the third parameter is the password. We cannot guarantee that the connection is successful. We will talk about exceptions later. Here we assume that the connection is successful.
$count = $db->exec("INSERT INTO foo SET name = 'heiyeluren',gender='male',time=NOW()");
echo $count;

Call our successfully connected PDO object to execute a query. This query is an operation to insert a record. Using the PDO::exec() method will return a result that affects the record, so we output this result. Finally, you still need to end the object resource:
$db = null;

By default, this is not a long connection. If you need a long connection to the database, you need to add a last parameter: array(PDO::ATTR_PERSISTENT => true) It becomes like this:
$db = new PDO($dsn, 'root', '', array(PDO::ATTR_PERSISTENT => true));

It’s as simple as one operation, maybe with There is not much difference from the previous one, but it is somewhat similar to ADOdb.

PDO Advanced Tutorial

If we want to extract data, we should use the data acquisition function. (The $db used below are all objects that have been connected above)

Copy code The code is as follows:

< ?php
　foreach($db->query("SELECT * FROM foo")){
print_r($row);
　}
?>

We can also use this acquisition method:

Copy code The code is as follows:

　$ rs = $db->query("SELECT * FROM foo");
while($row = $rs->fetch()){
print_r($row);
　}
?>

If you want to get all the data into the array at once, you can do this:

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$rs = $db->query("SELECT * FROM foo");
$result_arr = $rs->fetchAll();
print_r($result_arr);
?>

The output result is as follows:

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Array
([0] => Array(
[id] => 1
[0] => 1
[name] => ; heiyeluren
　[1] => heiyeluren
　[gender] => male
　[2] => male
　[time] => 2006-10-28 23:14: 23
　[3] => 2006-10-28 23:14:23
)
}

Let’s look at the records inside, both numeric index and associated index , a waste of resources, we only need to associate the index:

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$db->setAttribute(PDO::ATTR_CASE, PDO::CASE_UPPER);
$rs = $db->query("SELECT * FROM foo");
$rs->setFetchMode(PDO ::FETCH_ASSOC);
$result_arr = $rs->fetchAll();
print_r($result_arr);
?>

Look at the above code, setAttribute () method is to set some attributes. The main attributes are: PDO::ATTR_CASE, PDO::ATTR_ERRMODE, etc. What we need to set here is PDO::ATTR_CASE, that is, when we use the associated index to obtain the data set, the associated index is in uppercase Or lowercase, there are several options:

PDO::CASE_LOWER -- Force column names to be lowercase
PDO::CASE_NATURAL -- Column names are in the original way
PDO::CASE_UPPER -- Force Column names are capitalized

We use the setFetchMode method to set the type of return value for obtaining the result set. The same types are:

PDO::FETCH_ASSOC -- Associative array form
PDO: :FETCH_NUM -- Numeric index array form
PDO::FETCH_BOTH -- Both array forms are available, this is the default
PDO::FETCH_OBJ -- In object form, similar to the previous mysql_fetch_object()

Of course, generally we use PDO::FETCH_ASSOC. What to use depends on your own needs. For other acquisition types, refer to the manual.

In addition to the above method of obtaining data, there is also this:

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$rs = $db->prepare("SELECT * FROM foo");
$rs->execute();
while($row = $rs->fetch()){
print_r($row);
}
?>

Actually, it’s almost the same. If you want to get the result of a field in a specified record, you can use PDOStatement::fetchColumn():

Copy code The code is as follows:

$rs = $db->query("SELECT COUNT(*) FROM foo");
$col = $rs->fetchColumn();
echo $col;
?>

Generally, fetchColumn() is used for count statistics or some records that only require a single field are easy to operate.

Simple summary
The query operations are mainly PDO::query(), PDO::exec(), PDO::prepare(). PDO::query() is mainly used for operations that return recorded results, especially SELECT operations. PDO::exec() is mainly used for operations that do not return a result set, such as INSERT, UPDATE, DELETE and other operations. It returns The result is the number of columns affected by the current operation. PDO::prepare() is mainly a preprocessing operation. You need to use $rs->execute() to execute the SQL statement in the preprocessing. This method can bind parameters and is quite powerful. It cannot be explained simply in this article. You can refer to the manual and other documentation. The main operations for obtaining the result set are: PDOStatement::fetchColumn(), PDOStatement::fetch(), PDOStatement::fetchALL(). PDOStatement::fetchColumn() is a field of the first record specified in the fetch result. The default is the first field. PDOStatement::fetch() is used to obtain a record, and PDOStatement::fetchAll() is used to obtain all record sets into one. To obtain the results, you can set the type of the required result set through PDOStatement::setFetchMode.

There are two other peripheral operations, one is PDO::lastInsertId() and PDOStatement::rowCount(). PDO::lastInsertId() returns the last insertion operation, and the primary key column type is the last auto-increment ID. PDOStatement::rowCount() is mainly used for the result set affected by the DELETE, INSERT, and UPDATE operations of PDO::query() and PDO::prepare(), and is invalid for the PDO::exec() method and SELECT operations.

From the above usage, we can see that PDO is indeed powerful. There are also some other things that I have not mentioned, such as binding parameters, preprocessing, stored procedures, transaction processing and other functions. In addition, there are different data expansion DSN structures. Oracle database itself has many special things that require in-depth study and understanding. This article only briefly describes some introductory knowledge, which can be regarded as a simple understanding of PDO.

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