PHP magic method: __construct __destruct
From php5 and later versions, classes can use magic methods. PHP stipulates that methods starting with two underscores (__) are reserved as magic methods, so it is recommended that function names do not start with __ unless it is to overload existing magic methods.
The existing magic methods in PHP include __construct, __destruct, __call, __get, __set, __isset, __unset, __sleep, __wakeup, __toString, __set_state and __clone.
This section will talk about __construct, __destruct:
__construct() - This method is called every time a new object is created
__destruct() - Executed when all references to the object are deleted or when the object is explicitly destroyed
<?php
/**
* 清晰的认识__construct() __destruct
*/
class Example {
public static $link;
//在类实例化的时候自动加载__construct这个方法
public function __construct($localhost, $username, $password, $db) {
self::$link = mysql_connect($localhost, $username, $password);
if (mysql_errno()) {
die('错误:' . mysql_error());
}
mysql_set_charset('utf8');
mysql_select_db($db);
}
/**
* 通过__construct链接好数据库然后执行sql语句......
*/
//当类需要被删除或者销毁这个类的时候自动加载__destruct这个方法
public function __destruct() {
echo '<pre class="brush:php;toolbar:false">';
var_dump(self::$link);
mysql_close(self::$link);
var_dump(self::$link);
}
}
$mysql = new Example('localhost', 'root', 'root', 'test');
result:
resource(2) of type (mysql link) resource(2) of type (Unknown)
The above introduces the PHP magic method: __construct __destruct, including the content of PHP magic method. I hope it will be helpful to friends who are interested in PHP tutorials.
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