PHP features both a procedural API and an OOP one. For example, mysqli extension has both the native function mysqli_connect and the OOP method mysqli::__construct. Both API produce the same result. For example, the procedural style :
<?php
$link = mysqli_connect('localhost', 'my_user', 'my_password', 'my_db');
if (!$link) {
die('Connect Error (' . mysqli_connect_errno() . ') ';
}
echo 'Success... ' . mysqli_get_host_info($link) . "\n";
mysqli_close($link);
?>And the OOP Style :
<?php
try {
$db = new mysqli('localhost', 'my_user', 'my_password', 'my_db');
} catch (Exception $e) {
die('Connect Error (' . $db->errorno . ') ';
}
echo 'Success... ' . $db->host_info . "\n";
$db->close();
?>One of the main difference between the two styles, is the handling of the resource. Procedural style requires the call of an initialization function (here, mysqli_connect), which returns a resource. Resources are a old object of the PHP world, which are needed but can't really do much on their own. They are always requested as the first argument of the related family of functions, until they are closed with function like mysqli_close.
On the other hand, OOP style provides an object and a wealth of methods to manipulate it. Method names are closely related to their procedural counterpart : mysqli_prepare is called mysqli::prepare in OOP. Most of the time, the prefix is simply removed. In reality, the old resource is hidden inside the object. The main change is that every method is now freed of the first argument : since it is already inside the object, there is no more need to pass it as the first argument.
Some PHP extensions have no OOP equivalent : array and number manipulations. Those, of course, will require the procedural API. On the other hand, a large number of extensions now comes with an OOP interface, and no procedural one, such as ext/phar or ext/zmq.
It is recommended to use the object approach whenever possible.
The following are considered a warning :
<?php
$link = mysqli_connect('localhost', 'my_user', 'my_password', 'my_db');
?>The following are OK :
<?php
try {
$db = new mysqli('localhost', 'my_user', 'my_password', 'my_db');
} catch (Exception $e) {
die('Connect Error (' . $db->errorno . ') ';
}
?>If the project doesn't use any OOP feature, it may ignore this rule.