search
HomeBackend DevelopmentPHP TutorialPHP system constant magic method description and magic variable usage example summary

System constants

FILE Current file name
LINE Current line number
FUNCTION Current function name
CLASS Current class name
METHOD Current object method Name

Detailed analysis

1. FILE

The full path and file name of the file. If used in an included file, returns the included file name. Since PHP 4.0.2, FILE always contains an absolute path (or the resolved absolute path in the case of a symbolic link), while versions before that sometimes contained a relative path.
PHP constant dirname(file)
FILE: Known as PHPmagic constant, returns the full path and file name of the currently executing PHP script, including an absolute path

1 ) The dirname(FILE) function returns the path where the script is located. Update the network
For example, the file b.php contains the following content:

<?php   
$basedir = dirname(FILE);   
echo $basedir  
//将在页面打印出一个这个文件所在绝对路径!  
?>

This is equivalent to the usage of server.mappth in asp
If b.php is required by the a.php file in other directories Or include to quote. The content of the variable $basedir is still the path to the folder where b.php is located. Instead of becoming the directory where the a.php file is located.

2) dirname(FILE) generally returns a directory structure from the current directory where the file is located to the system root directory.
The current file name will not be returned. dirname(FILE) may also return one. (current directory) [The reason is that the b.php file is in the default WEB directory of http.conf or PHP Configure development environment

<?php
/**
在你的公用的配置文件中,来设置你的根目录,这样就不用担心经常搬家了。
*/
define(&#39;ROOT_PATH&#39;, dirname(FILE) . DIRECTORY_SEPARATOR);
echo ROOT_PATH;
echo "<br>";
echo FILE;
echo "<br>";
echo dirname(FILE);
echo "<br>";
echo dirname(dirname(FILE));
?>


2. LINE

The current line number in the file. This variable is quite useful when debugging errors. At other times, it is of little use.

<?php
echo LINE;  //显示,LINE所在的行号
?>


3. CLASS
The name of the class, the result returned by PHP5 It is case-sensitive

<?php
class base_class
{
function say_a()
{
echo "&#39;a&#39; – said the " . CLASS . "<br/>";
}
function say_b()
{
echo "&#39;b&#39; – said the " . get_class($this) . "<br/>";
}
}
class derived_class extends base_class
{
function say_a()
{
parent::say_a();
echo "&#39;a&#39; – said the " . CLASS . "<br/>";
}
function say_b()
{
parent::say_b();
echo "&#39;b&#39; – said the " . get_class($this) . "<br/>";
}
}
$obj_b = new derived_class();
$obj_b->say_a();
echo "<br/>";
$obj_b->say_b();
?>

The result is:

&#39;a&#39; – said the base_class
&#39;a&#39; – said the derived_class
&#39;b&#39; – said the  derived_class
&#39;b&#39; – said the derived_class

Sometimes, we can use get_class instead of CLASS

4. FUNCTION and METHOD

FUNCTION: Function name, the result returned in php5 is case-sensitive
METHOD: Function name in the method, the result returned in php5 is case-sensitive
Two They are both the names of the methods, what's the difference?

<?php
class test
{
function a()
{
echo FUNCTION;
echo "<br>";
echo METHOD;
}
}
function good (){
echo FUNCTION;
echo "<br>";
echo METHOD;
}
$test = new test();
$test->a();
echo "<br>";
good();
?>

Return result:

a
test::a
good
good

Compared with the isolated function, both can take out the function name, there is no difference. If it is a method in the class, FUNCTION can only Get the method name of the class, and METHOD can not only get the method name, but also the directory where the class name

5. DIR

is located. If used within an included file, returns the directory where the included file is located. It is equivalent to dirname(FILE). Directory names do not include the trailing slash unless they are the root directory. (New in PHP 5.3.0)
If you want to use DIR in versions before 5.3, you can do this

<?php
if(!defined(&#39;DIR&#39;)) {
$iPos = strrpos(FILE, "/");
define("DIR", substr(FILE, 0, $iPos) . "/");
}
?>

6. NAMESPACE

currentThe name of the namespace (case sensitive). This constant is defined at compile time (new in PHP 5.3.0)

7. STATIC

#When you call the static method of class, return the class name, case sensitive. If called in inheritance, the inherited class name can be returned regardless of whether it is defined in inheritance.

<?php
//php5.3
class Model
{
public static function find()
{
echo STATIC;
}
}
class Product extends Model {}
class User extends Model {}
Product::find(); // "Product"
User::find(); // "User"
?>

The above is the detailed content of PHP system constant magic method description and magic variable usage example summary. For more information, please follow other related articles on the PHP Chinese website!

Statement
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn
PHP Performance Tuning for High Traffic WebsitesPHP Performance Tuning for High Traffic WebsitesMay 14, 2025 am 12:13 AM

ThesecrettokeepingaPHP-poweredwebsiterunningsmoothlyunderheavyloadinvolvesseveralkeystrategies:1)ImplementopcodecachingwithOPcachetoreducescriptexecutiontime,2)UsedatabasequerycachingwithRedistolessendatabaseload,3)LeverageCDNslikeCloudflareforservin

Dependency Injection in PHP: Code Examples for BeginnersDependency Injection in PHP: Code Examples for BeginnersMay 14, 2025 am 12:08 AM

You should care about DependencyInjection(DI) because it makes your code clearer and easier to maintain. 1) DI makes it more modular by decoupling classes, 2) improves the convenience of testing and code flexibility, 3) Use DI containers to manage complex dependencies, but pay attention to performance impact and circular dependencies, 4) The best practice is to rely on abstract interfaces to achieve loose coupling.

PHP Performance: is it possible to optimize the application?PHP Performance: is it possible to optimize the application?May 14, 2025 am 12:04 AM

Yes,optimizingaPHPapplicationispossibleandessential.1)ImplementcachingusingAPCutoreducedatabaseload.2)Optimizedatabaseswithindexing,efficientqueries,andconnectionpooling.3)Enhancecodewithbuilt-infunctions,avoidingglobalvariables,andusingopcodecaching

PHP Performance Optimization: The Ultimate GuidePHP Performance Optimization: The Ultimate GuideMay 14, 2025 am 12:02 AM

ThekeystrategiestosignificantlyboostPHPapplicationperformanceare:1)UseopcodecachinglikeOPcachetoreduceexecutiontime,2)Optimizedatabaseinteractionswithpreparedstatementsandproperindexing,3)ConfigurewebserverslikeNginxwithPHP-FPMforbetterperformance,4)

PHP Dependency Injection Container: A Quick StartPHP Dependency Injection Container: A Quick StartMay 13, 2025 am 12:11 AM

APHPDependencyInjectionContainerisatoolthatmanagesclassdependencies,enhancingcodemodularity,testability,andmaintainability.Itactsasacentralhubforcreatingandinjectingdependencies,thusreducingtightcouplingandeasingunittesting.

Dependency Injection vs. Service Locator in PHPDependency Injection vs. Service Locator in PHPMay 13, 2025 am 12:10 AM

Select DependencyInjection (DI) for large applications, ServiceLocator is suitable for small projects or prototypes. 1) DI improves the testability and modularity of the code through constructor injection. 2) ServiceLocator obtains services through center registration, which is convenient but may lead to an increase in code coupling.

PHP performance optimization strategies.PHP performance optimization strategies.May 13, 2025 am 12:06 AM

PHPapplicationscanbeoptimizedforspeedandefficiencyby:1)enablingopcacheinphp.ini,2)usingpreparedstatementswithPDOfordatabasequeries,3)replacingloopswitharray_filterandarray_mapfordataprocessing,4)configuringNginxasareverseproxy,5)implementingcachingwi

PHP Email Validation: Ensuring Emails Are Sent CorrectlyPHP Email Validation: Ensuring Emails Are Sent CorrectlyMay 13, 2025 am 12:06 AM

PHPemailvalidationinvolvesthreesteps:1)Formatvalidationusingregularexpressionstochecktheemailformat;2)DNSvalidationtoensurethedomainhasavalidMXrecord;3)SMTPvalidation,themostthoroughmethod,whichchecksifthemailboxexistsbyconnectingtotheSMTPserver.Impl

See all articles

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

Video Face Swap

Video Face Swap

Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

Zend Studio 13.0.1

Zend Studio 13.0.1

Powerful PHP integrated development environment

SublimeText3 Linux new version

SublimeText3 Linux new version

SublimeText3 Linux latest version

SAP NetWeaver Server Adapter for Eclipse

SAP NetWeaver Server Adapter for Eclipse

Integrate Eclipse with SAP NetWeaver application server.

MinGW - Minimalist GNU for Windows

MinGW - Minimalist GNU for Windows

This project is in the process of being migrated to osdn.net/projects/mingw, you can continue to follow us there. MinGW: A native Windows port of the GNU Compiler Collection (GCC), freely distributable import libraries and header files for building native Windows applications; includes extensions to the MSVC runtime to support C99 functionality. All MinGW software can run on 64-bit Windows platforms.

DVWA

DVWA

Damn Vulnerable Web App (DVWA) is a PHP/MySQL web application that is very vulnerable. Its main goals are to be an aid for security professionals to test their skills and tools in a legal environment, to help web developers better understand the process of securing web applications, and to help teachers/students teach/learn in a classroom environment Web application security. The goal of DVWA is to practice some of the most common web vulnerabilities through a simple and straightforward interface, with varying degrees of difficulty. Please note that this software