Backend Development
PHP Tutorial
Detailed explanation of the usage and precautions of the static keyword in PHP
Detailed explanation of the usage and precautions of the static keyword in PHP
PHP static keyword is used to define static methods and properties, which can be used to delay static binding in classes and modify them in functions variable.
1: Let’s first talk about the use of static in functions;
function add(){
static $a = 0;
echo $a,"<br />";
$a++;
}The role of static here is similar to the role of static in C. It ensures that the $a variable will only be initialized when add() is called for the first time, but it should be noted that defining static variables When assigning an initial value, you do not need to assign an initial value or you can give an initial value. However, when assigning an initial value, you cannot use expression or call a function to assign a value, otherwise an error will be reported.
Another thing to note is that static variables will not store references, as follows:
function get_obj_ref(){
static $obj = null;
echo 'Ststic obj:',"<br />";
var_dump($obj);
if(is_null($obj)){
$obj = &new stdClass();
}
return $obj;
}
$obj = get_obj_ref();
$obj2 = get_obj_ref();
function get_obj_noref(){
static $obj = null;
echo 'Ststic obj:',"<br />";
var_dump($obj);
if(is_null($obj)){
$obj = new stdClass();
}
return $obj;
}
$obj = get_obj_noref();
$obj2 = get_obj_noref();When static is stored When quoting, the value of the variable is not saved after calling the function a second time, and a Deprecated error will be reported when running the above program, that is, the usage of return reference value assignment has been abandoned.
2: Delayed static binding of static in the class;
Delayed static Binding refers to allowing the called class to be referenced in the context of a static inheritance. Delayed binding means: static:: is no longer the class in which the current method is defined, but the class in which it is actually run. Note: It can be used for (but not limited to) static method calls.
In addition to the simple static delayed binding usage, there is also a forward call, that is, using self::, parent::, static:: and forward_static_call( ) (This function can only be called in a method) will forward the calling information, as follows:
##
class A {
public static function foo() {
static::who();
}
public static function who() {
echo CLASS."\n";
}
}
class B extends A {
public static function test() {
A::foo();
parent::foo();
self::foo();
}
public static function who() {
echo CLASS."\n";
}
}
class C extends B {
public static function who() {
echo CLASS."\n";
}
}
C::test();The result obtained here is A C C. Obviously, when calling parent::foo(), the runtime calling class is still used.
Another thing to note is: Only static classes that are explicitly declared are subordinate and subclasses.
The following part of the content refers to this blog post:Click to open the link:PHP static inheritance
<span style="font-size:18px;">class A {
protected static $var1 = null;
protected static $var2 = null;
public static function test(){
if(!static::$var2){
static::$var2 = static::$var1;
}
echo get_called_class().' '.static::$var2.'
';
}
}
class B extends A {
protected static $var1 = 'b';
}
class C extends A {
protected static $var1 = 'c';
}
B::test();
C::test(); </span>The result obtained here is b b. Here, class B first called the test() method, and the $var2 variable has been assigned a value after the call. However, class C has not defined its own $var2 variable, and the $var2 variable value already exists in the parent class, so it can be used directly. If in class B If $var2 variable is explicitly defined in , the result will be different.
The above is the detailed content of Detailed explanation of the usage and precautions of the static keyword in PHP. For more information, please follow other related articles on the PHP Chinese website!
Hot AI Tools
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Undress AI Tool
Undress images for free
Clothoff.io
AI clothes remover
Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!
Hot Article
Hot Tools
Notepad++7.3.1
Easy-to-use and free code editor
SublimeText3 Chinese version
Chinese version, very easy to use
Zend Studio 13.0.1
Powerful PHP integrated development environment
Dreamweaver CS6
Visual web development tools
SublimeText3 Mac version
God-level code editing software (SublimeText3)
Hot Topics
1664
14
1423
52
1318
25
1268
29
1248
24
Explain JSON Web Tokens (JWT) and their use case in PHP APIs.
Apr 05, 2025 am 12:04 AM
JWT is an open standard based on JSON, used to securely transmit information between parties, mainly for identity authentication and information exchange. 1. JWT consists of three parts: Header, Payload and Signature. 2. The working principle of JWT includes three steps: generating JWT, verifying JWT and parsing Payload. 3. When using JWT for authentication in PHP, JWT can be generated and verified, and user role and permission information can be included in advanced usage. 4. Common errors include signature verification failure, token expiration, and payload oversized. Debugging skills include using debugging tools and logging. 5. Performance optimization and best practices include using appropriate signature algorithms, setting validity periods reasonably,
PHP Program to Count Vowels in a String
Feb 07, 2025 pm 12:12 PM
A string is a sequence of characters, including letters, numbers, and symbols. This tutorial will learn how to calculate the number of vowels in a given string in PHP using different methods. The vowels in English are a, e, i, o, u, and they can be uppercase or lowercase. What is a vowel? Vowels are alphabetic characters that represent a specific pronunciation. There are five vowels in English, including uppercase and lowercase: a, e, i, o, u Example 1 Input: String = "Tutorialspoint" Output: 6 explain The vowels in the string "Tutorialspoint" are u, o, i, a, o, i. There are 6 yuan in total
Explain late static binding in PHP (static::).
Apr 03, 2025 am 12:04 AM
Static binding (static::) implements late static binding (LSB) in PHP, allowing calling classes to be referenced in static contexts rather than defining classes. 1) The parsing process is performed at runtime, 2) Look up the call class in the inheritance relationship, 3) It may bring performance overhead.
What are PHP magic methods (__construct, __destruct, __call, __get, __set, etc.) and provide use cases?
Apr 03, 2025 am 12:03 AM
What are the magic methods of PHP? PHP's magic methods include: 1.\_\_construct, used to initialize objects; 2.\_\_destruct, used to clean up resources; 3.\_\_call, handle non-existent method calls; 4.\_\_get, implement dynamic attribute access; 5.\_\_set, implement dynamic attribute settings. These methods are automatically called in certain situations, improving code flexibility and efficiency.
PHP and Python: Comparing Two Popular Programming Languages
Apr 14, 2025 am 12:13 AM
PHP and Python each have their own advantages, and choose according to project requirements. 1.PHP is suitable for web development, especially for rapid development and maintenance of websites. 2. Python is suitable for data science, machine learning and artificial intelligence, with concise syntax and suitable for beginners.
PHP in Action: Real-World Examples and Applications
Apr 14, 2025 am 12:19 AM
PHP is widely used in e-commerce, content management systems and API development. 1) E-commerce: used for shopping cart function and payment processing. 2) Content management system: used for dynamic content generation and user management. 3) API development: used for RESTful API development and API security. Through performance optimization and best practices, the efficiency and maintainability of PHP applications are improved.
PHP: A Key Language for Web Development
Apr 13, 2025 am 12:08 AM
PHP is a scripting language widely used on the server side, especially suitable for web development. 1.PHP can embed HTML, process HTTP requests and responses, and supports a variety of databases. 2.PHP is used to generate dynamic web content, process form data, access databases, etc., with strong community support and open source resources. 3. PHP is an interpreted language, and the execution process includes lexical analysis, grammatical analysis, compilation and execution. 4.PHP can be combined with MySQL for advanced applications such as user registration systems. 5. When debugging PHP, you can use functions such as error_reporting() and var_dump(). 6. Optimize PHP code to use caching mechanisms, optimize database queries and use built-in functions. 7
The Enduring Relevance of PHP: Is It Still Alive?
Apr 14, 2025 am 12:12 AM
PHP is still dynamic and still occupies an important position in the field of modern programming. 1) PHP's simplicity and powerful community support make it widely used in web development; 2) Its flexibility and stability make it outstanding in handling web forms, database operations and file processing; 3) PHP is constantly evolving and optimizing, suitable for beginners and experienced developers.
