A brief introduction to php magic functions and magic constants

This article mainly introduces to you the relevant knowledge of PHP magic functions and magic constants. Friends who need it can refer to it. I hope it can help everyone.

php magic function

1. __construct()

Called when instantiating an object,
When __construct and a function with the class name and function name exist at the same time, __construct will be called, and the other will not be called.

2. __destruct()
Called when an object is deleted or the object operation terminates.

3. __call()
The object calls a method.
If the method exists, it will be called directly;
If it does not exist, the __call function will be called.

4. __get()
When reading the attributes of an object,
If the attribute exists, the attribute value will be returned directly;
If it does not exist, the __get function will be called.

5. __set()
When setting the attributes of an object,
If the attribute exists, the value will be assigned directly;
If it does not exist, the __set function will be called.

6. __toString()
Called when printing an object. Such as echo $obj; or print $obj;

7. __clone()
Called when cloning an object. For example: $t=new Test();$t1=clone $t;

8. __sleep()
Serialize is called before. If the object is relatively large and you want to delete a few things before serializing, you can consider this function.

9. __wakeup()
is called when unserialize and does some object initialization work.

10. __isset()
Called when detecting whether an object's attributes exist. For example: isset($c->name).

11. __unset()
Called when unsetting the properties of an object. For example: unset($c->name).

12. __set_state()
Called when var_export is called. Use the return value of __set_state as the return value of var_export.

13. __autoload()
When instantiating an object, if the corresponding class does not exist, this method is called.

php magic constant

1. __LINE__
Returns the current line number in the file.

2. __FILE__
Returns the full path and file name of the file. If used in an include file, returns the include file name. As of PHP 4.0.2, __FILE__ always contains an absolute path, while versions before that sometimes contained a relative path.

3. __FUNCTION__
Returns the function name (newly added 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.

4. __CLASS__
Returns 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.

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

(1) First introduction to magic methods
Php5.0 has provided us with many object-oriented features since its release, especially many easy-to-use magic methods. These magic methods allow us to Simplify our coding and better design our systems. Today we will learn about the magic methods provided by php5.0.

Comparison of php using magic functions and not using magic functions

/**
* use magic 0.31868386268616s
* not use magic 0.11876797676086s
*/
class Test {
  private $varstr = "123";

  function __get($name) {
    return $this->varstr;
  }
}

function microtime_float()
{
  list($usec, $sec) = explode(" ", microtime());
  return ((float)$usec + (float)$sec);
}

$time_start = microtime_float();

$i = 0;
while ($i<100000) {
  $i++;
  $t = new Test();
  $t->varstr;
}

$time_end = microtime_float();
$time = $time_end - $time_start;

echo "Did nothing in $time seconds\n";

It is recommended to use PHP magic functions as little as possible.

Related recommendations:

About PHP magic function performance

How to use magic function? Summary of usage of magic function examples

PHP Detailed analysis of magic function performance code

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