PHP magic methods:
__construct(), __destruct(), __call(), __callStatic(), __get(), __set(), __isset(), __unset(), __sleep(), __wakeup(), Methods such as __toString(), __invoke(), __set_state(), __clone() and __debugInfo() are called "Magic methods" in PHP. You cannot use these method names when naming your own class methods unless you want to use their magic functionality.
__construct(),类的构造函数 __destruct(),类的析构函数 __call(),在对象中调用一个不可访问方法(私有或者不存在)时调用 __callStatic(),用静态方式中调用一个不可访问方法时调用 __get(),获得一个类的成员变量时调用 __set(),设置一个类的成员变量时调用 __isset(),当对不可访问属性调用isset()或empty()时调用 __unset(),当对不可访问属性调用unset()时被调用。 __sleep(),执行serialize()时,先会调用这个函数 __wakeup(),执行unserialize()时,先会调用这个函数 __toString(),类被当成字符串时的回应方法 __invoke(),调用函数的方式调用一个对象时的回应方法 __set_state(),调用var_export()导出类时,此静态方法会被调用。 __clone(),当对象复制完成时调用
__construct() and __destruct()
The constructor __construct() is called when the object is created, and the destructor __destruct() is called when the object dies
<?php   class ConDes {     protected $a = '';     function __construct(){         echo '在构造函数中<br>'; } function __destruct(){ echo '在析构函数中<br>'; } } $val = new ConDes(); unset($val); ?><pre name="code" class="php">output:
In the constructor and in the destructor
__call() and __callStatic() are called when an inaccessible method is called in the object. The latter is a static method.
<?php   class MethodTest   {     public function __call ($name, $arguments) {     var_dump($arguments);         echo "object method $name and ".implode(',',$arguments)."<br>"; } public static function __callStatic ($name, $arguments) { echo "static method $name and ".implode(',',$arguments)."<br>"; } } $obj = new MethodTest; $obj->runTest('in object context','another arg'); MethodTest::runTest('in static context'); ?>output:
array (size=2)
0 => string 'in object context' (length=17)
1 => string 'another arg' (length=11)
object method runTest and in object context,another arg
static method runTest and in static context
__get(), __set(), __isset() and __unset()
These two functions are called when getting an inaccessible class member variable or setting an inaccessible class member variable .
<?php class MethodTest { private $data = array(); private $a = ''; public $bbb = ''; public function __set($name, $value){ $this->data[$name] = $value; echo '__set'; var_dump($this->data); } public function __get($name){ echo '__get'; var_dump($this->data); if(array_key_exists($name, $this->data)) return $this->data[$name]; return NULL; } public function __isset($name){ echo '__isset'; return isset($this->data[$name]); } public function __unset($name){ echo '__unset'; unset($this->data[$name]); } } $in = new MethodTest(); $in->a = 'aaaa'; $aaa = $in->a; $res = isset($in->c)? 'set':'not set'; echo '<br>'.$res.'<br>'; unset($in->a); ?>output:
__set
array (size=1)
'a' => string 'aaaa' (length=4)
__get
array (size=1)
'a' => string 'aaaa' (length=4)
__isset
not set
__unset
__sleep() and __wakeup()
When we execute serialize() and unserialize(), these two functions will be called first. For example, when we serialize an object, the object has a database link. If we want to restore the link state during deserialization, we can restore the link by reconstructing these two functions.
<span></span>
<?php class Connection {     public $link;     private $server, $username, $password, $db;          public function __construct($server, $username, $password, $db)     {         $this->server = $server; $this->username = $username; $this->password = $password; $this->db = $db; $this->connect(); } private function connect() { $this->link = mysql_connect($this->server, $this->username, $this->password); mysql_select_db($this->db, $this->link); } public function __sleep() { echo 'sleep<br>'; return array('server', 'username', 'password', 'db'); } public function __wakeup() { echo 'wakeup<br>'; $this->connect(); } } $a = new Connection('localhost','mosi','moshi','test'); $sql = 'select id,username from user limit 1'; $res = mysql_query($sql,$a->link); $res = mysql_fetch_array($res); var_dump($res); $sres = serialize($a); mysql_close($a->link); //unset($a); $unsres = unserialize($sres); var_dump($unsres); $sql = 'select id,username from user limit 1'; $ress = mysql_query($sql,$unsres->link); $ress = mysql_fetch_array($ress); var_dump($ress); ?>output:
<span>array (size=4)<br> 0 => string '1' (length=1)<br> 'id' => string '1' (length=1)<br> 1 => string 'm0sh1' (length =5)<br> 'username' => string 'm0sh1' (length=5)<br>sleep<br>wakeup<br>object(Connection)[2]<br> public 'link' => resource(6, mysql link)<br> private 'server ' => string 'localhost' (length=9)<br> private 'username' => string 'moshi' (length=4)<br> private 'password' => string 'moshi' (length=5)<br> private ' db' => string 'test' (length=4)<br>array (size=4)<br> 0 => string '1' (length=1)<br> 'id' => string '1' (length=1 )<br> 1 => string 'm0sh1' (length=5)<br> 'username' => string 'm0sh1' (length=5)</span>
<span>__toString()<br> when the object is treated as a string response method. For example, using echo $obj;</span>
<span></span>
<?php class TestClass { public function __toString() { return 'this is a object'; } } $class = new TestClass(); echo $class; ?>output:
<span></span>
<span></span>
this is a object
This method can only return a string, and exceptions cannot be thrown in this method, otherwise a fatal error will occur.
__invoke()
The response method when calling an object by calling a function.
<?php class Invoke{ public function __invoke(){ echo 'in invoke<br>'; } } class noInvoke{ } $obj = new Invoke(); $obj(); var_dump(is_callable($obj)); $obj2 = new noInvoke(); //$obj2(); var_dump(is_callable($obj2));
Output:
in invoke
boolean true
boolean false
__set_state()
This static method will be called when var_export() is called to export a class.
<?php class A { public $var1; public $var2; public static function __set_state ($arr) { $obj = new A; $obj->var1 = 'var11'; $obj->var2 = $arr['var2']; return $obj; } } $a = new A; $a->var1 = 5; $a->var2 = 'foo'; var_dump($a); var_export($a); eval('$ress = '.var_export($a,true).';'); var_dump($ress); ?>
Output:
object(A)[1]
public 'var1' => int 5
public 'var2' => string 'foo' (length=3)
A::__set_state(array( 'var1' => 5, 'var2' => 'foo', ))
object(A)[2]
public 'var1' => string 'var11' (length=5)
public 'var2' => string 'foo' (length=3)
__clone()
Called when the object copy is completed.
<?php class Singleton { private static $_instance = NULL; // 私有构造方法 private function __construct() {} public static function getInstance() { if (is_null(self::$_instance)) { self::$_instance = new Singleton(); } return self::$_instance; } // 防止克隆实例 public function __clone(){ die('Clone is not allowed error: ' . E_USER_ERROR); } } $a = Singleton::getInstance(); $b = Singleton::getInstance(); if( $a === $b ){ echo 'equal<br>'; } $c = clone $b; ?>
Output:
equal
Clone is not allowed error: 256
PHP Magic Constants: Introduction here
The above has introduced the magic methods in PHP, including the relevant content. I hope it will be helpful to friends who are interested in PHP tutorials.

PHPsessionstrackuserdataacrossmultiplepagerequestsusingauniqueIDstoredinacookie.Here'showtomanagethemeffectively:1)Startasessionwithsession_start()andstoredatain$_SESSION.2)RegeneratethesessionIDafterloginwithsession_regenerate_id(true)topreventsessi

In PHP, iterating through session data can be achieved through the following steps: 1. Start the session using session_start(). 2. Iterate through foreach loop through all key-value pairs in the $_SESSION array. 3. When processing complex data structures, use is_array() or is_object() functions and use print_r() to output detailed information. 4. When optimizing traversal, paging can be used to avoid processing large amounts of data at one time. This will help you manage and use PHP session data more efficiently in your actual project.

The session realizes user authentication through the server-side state management mechanism. 1) Session creation and generation of unique IDs, 2) IDs are passed through cookies, 3) Server stores and accesses session data through IDs, 4) User authentication and status management are realized, improving application security and user experience.

Tostoreauser'snameinaPHPsession,startthesessionwithsession_start(),thenassignthenameto$_SESSION['username'].1)Usesession_start()toinitializethesession.2)Assigntheuser'snameto$_SESSION['username'].Thisallowsyoutoaccessthenameacrossmultiplepages,enhanc

Reasons for PHPSession failure include configuration errors, cookie issues, and session expiration. 1. Configuration error: Check and set the correct session.save_path. 2.Cookie problem: Make sure the cookie is set correctly. 3.Session expires: Adjust session.gc_maxlifetime value to extend session time.

Methods to debug session problems in PHP include: 1. Check whether the session is started correctly; 2. Verify the delivery of the session ID; 3. Check the storage and reading of session data; 4. Check the server configuration. By outputting session ID and data, viewing session file content, etc., you can effectively diagnose and solve session-related problems.

Multiple calls to session_start() will result in warning messages and possible data overwrites. 1) PHP will issue a warning, prompting that the session has been started. 2) It may cause unexpected overwriting of session data. 3) Use session_status() to check the session status to avoid repeated calls.

Configuring the session lifecycle in PHP can be achieved by setting session.gc_maxlifetime and session.cookie_lifetime. 1) session.gc_maxlifetime controls the survival time of server-side session data, 2) session.cookie_lifetime controls the life cycle of client cookies. When set to 0, the cookie expires when the browser is closed.


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