Summary of tutorials on php magic variables and magic functions-PHP Tutorial-php.cn

Summary of tutorials on php magic variables and magic functions

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Release： 2016-07-25 08:51:44

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echo 'This is the " ' . __LINE__ . ' " line';
?>

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The output result is: This is line “2”

__FILE__ The full path and filename 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.

Example:

echo 'The file is located at " ' . __FILE__ . ' " ';
?>

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The output result is: The file is located at " E:wampwwwtestindex.php "

__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)

Example:

echo 'The file is located at " ' . __DIR__ . ' " ';
?>

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The output result is: The file is located at " E:wampwwwtest "

__FUNCTION__ Function name (new in PHP 4.3.0). Since PHP 5 this constant returns the name of the function as it was defined (case sensitive). In PHP 4 this value is always lowercase.

Example:

function test() {
echo 'The function is called:' . __FUNCTION__ ;
}
test();
?>

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The output result is: Function name: test

__CLASS__ The name of the class (new in PHP 4.3.0). Since PHP 5 this constant returns the name of the class when it was defined (case sensitive). In PHP 4 this value is always lowercase. The class name includes the scope in which it is declared (e.g. FooBar). Note that since PHP 5.4 __CLASS__ also works for traits. When used within a trait method, __CLASS__ is the name of the class that calls the trait method.

Example:

class test {
function _print() {
echo 'The class name is:' . __CLASS__ . "
";
echo 'The function name is:' . __FUNCTION__ ;
}
}
$t = new test();
$t->_print();
?>

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The output result is: Class name: test Function name: _print

__TRAIT__ The name of the trait (new in PHP 5.4.0). Since PHP 5.4.0, PHP implements a method of code reuse called traits. The trait name includes the scope in which it is declared (e.g. FooBar). Members inherited from the base class are overridden by the MyHelloWorld method in the inserted SayWorld Trait. Its behavior is consistent with the methods defined in the MyHelloWorld class. The order of precedence is that methods in the current class override trait methods, which in turn override methods in the base class.

Example:

class Base {
public function sayHello() {
echo 'Hello ';
}
}
{
public function sayHello() {
parent::sayHello();
echo 'World!';
}
}
class MyHelloWorld extends Base {
}
$o = new MyHelloWorld();
$o->sayHello();
?>

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Output : Hello World!

__METHOD__ The method name of the class (new in PHP 5.0.0). Returns the name of the method as it was defined (case-sensitive).

Example:

function test() {
echo 'The function is called:' . __METHOD__ ;
}
test();
?>

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The output result is: Function name: test

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

Example:

namespace MyProject;
echo 'The namespace is: "', __NAMESPACE__, '"'; // Output "MyProject"
?>

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The output result is: The namespace is: "MyProject"

Magic function __construct() Called when an object is instantiated, When __construct and a function with the class name exist at the same time, __construct will be called and the other will not be called. __destruct() Called when an object is deleted or when the object operation terminates. __call() The object calls a method, If the method exists, call it directly; If it does not exist, the __call function will be called. __get() When reading the properties of an object, If the attribute exists, the attribute value is returned directly; If it does not exist, the __get function will be called. __set() When setting the properties of an object, If the attribute exists, assign it directly; If it does not exist, the __set function will be called. __toString() Called when printing an object. Such as echo $obj; or print $obj; __clone() Called when cloning an object. For example: $t=new Test();$t1=clone $t; __sleep() serialize was called before. If the object is relatively large and you want to delete a little bit before serializing it, you can consider this function. __wakeup() It is called when unserialize is used to do some object initialization work. __isset() Called when checking whether an object's property exists. Such as: isset($c->name). __unset() Called when unsetting a property of an object. For example: unset($c->name). __set_state() Called when var_export is called. Use the return value of __set_state as the return value of var_export. __autoload() When instantiating an object, this method is called if the corresponding class does not exist.