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Detailed explanation of php magic variable usage examples, detailed explanation of php magic examples_PHP tutorial
Detailed explanation of php magic variable usage examples, detailed explanation of php magic examples_PHP tutorial
Detailed explanation of php magic variable usage examples, detailed explanation of php magic examples
The example in this article describes the usage of php magic variables, among which __DIR__ is new in php5.3 and is shared with everyone for your reference. The specific usage analysis is as follows:
System constants
__FILE__ current file name
__LINE__ Current line number
__FUNCTION__ Current function name
__CLASS__ current class name
__METHOD__ The method name of the current object
Detailed analysis
1. __FILE__
The full path and file name of the file. If used within an included file, returns the name of the included file. Since PHP 4.0.2, __FILE__ always contains an absolute path (or the resolved absolute path in the case of a symbolic link), whereas versions before that sometimes contained a relative path.
PHP constant dirname(__file__)
__FILE__: Known as PHP magic 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 network
For example, the file b.php contains the following content:
echo $basedir
//An absolute path to the file will be printed on the page!
?>
The test I did got the result: E:websiteothertestcms
This is equivalent to the usage of server.mappth in asp
If b.php is referenced by a.php file require or include in other directories. The content of the variable $basedir is still the path to the folder where b.php is located. Instead of becoming the directory where the a.php file is located.
2) dirname(__FILE__) generally returns a directory structure from the current directory where the file is located to the system root directory.
The current file name is not returned. dirname(__FILE__) may also return a . (current directory) [The reason is that the b.php file is in http.conf or the default WEB directory of the PHP configuration development environment
In your public configuration file, set your root directory so you don't have to worry about moving frequently.
*/
define('ROOT_PATH', dirname(__FILE__) . DIRECTORY_SEPARATOR);
echo ROOT_PATH;
echo "
";
echo __FILE__;
echo "
";
echo dirname(__FILE__);
echo "
";
echo dirname(dirname(__FILE__));
?>
2. __LINE__
The current line number in the file. This variable is quite useful when debugging errors. At other times, it is of little use. It is purely a personal opinion.
?>
3. __CLASS__
The name of the class, the results returned by PHP5 are case-sensitive
{
function say_a()
{
echo "'a' – said the " . __CLASS__ . "
";
}
function say_b()
{
echo "'b' – said the " . get_class($this) . "
";
}
}
class derived_class extends base_class
{
function say_a()
{
parent::say_a();
echo "'a' – said the " . __CLASS__ . "
";
}
function say_b()
{
parent::say_b();
echo "'b' – said the " . get_class($this) . "
";
}
}
$obj_b = new derived_class();
$obj_b->say_a();
echo "
";
$obj_b->say_b();
?>
The result is:
'a' – said the derived_class
'b' – said the derived_class
'b' – 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__: The function name in the method, the result returned in php5 is case-sensitive
Both are the names of the acquisition methods. What's the difference?
{
function a()
{
echo __FUNCTION__;
echo "
";
echo __METHOD__;
}
}
function good (){
echo __FUNCTION__;
echo "
";
echo __METHOD__;
}
$test = new test();
$test->a();
echo "
";
good();
?>
Return result:
a
test::a
good
good
Compared with an isolated function, both can extract the function name. There is no difference. If it is a method in a class, __FUNCTION__ can only extract the method name of the class, while __METHOD__ can not only extract the method name, but also the method name. class name
5. __DIR__
The directory where the file 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 prior to 5.3, you can do this
$iPos = strrpos(__FILE__, "/");
define("__DIR__", substr(__FILE__, 0, $iPos) . "/");
}
?>
6. __NAMESPACE__
The name of the current namespace (case sensitive). This constant is defined at compile time (new in PHP 5.3.0)
7. __STATIC__
When you call a static method of a class, the class name is returned, case-sensitive. If called in inheritance, the inherited class name can be returned regardless of whether it is defined in inheritance.
class Model
{
public static function find()
{
echo __STATIC__;
}
}
class Product extends Model {}
class User extends Model {}
Product::find(); // "Product"
User::find(); // "User"
?>
Additional: Magic method in php
__construct() When instantiating an object, this method of the object is first called.
__destruct() This method is called when an object is deleted or when the object operation terminates.
__get() is called when trying to read a property that does not exist.
__set() is called when trying to write a value to a property that does not exist.
__call() This method is called when trying to call a method that does not exist on the object.
__toString() is called when printing an object
__clone() is called when the object is cloned
__isset()
__unset()
__autoload($classname)
__sleep()
__wakeup()
I hope this article will be helpful to everyone’s PHP programming design.
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