php constructor and destructor

In PHP programming, there is a function called the constructor in object-oriented programming, which is a method that is automatically called when an object is created to complete class initialization.

Because this function will be automatically executed as soon as the PHP class is loaded, and generally the initialization work is placed in this function.

1. The constructor, like other functions, can pass parameters and set default parameter values.

2. The constructor can call properties and methods.

3. The constructor can be explicitly called by other methods.

In previous PHP versions, the constructor used the same name as the class name to initialize the object. However, it was later discovered that if you want to change the class name, you must also change its construction method, so in PHP5, it is used __construct( ) function to implement. __construct() is preceded by two underscores, do not think it is one underscore.

Corresponding to the constructor is the destructor. It is executed when an object becomes garbage or when the object is explicitly destroyed.

__destruct() destructor is executed when the garbage object is recycled.

1. Do not call the destructor of an object in the program.
2. The destructor cannot have parameters.
3. Usually php will automatically perform garbage collection after the program ends.

Because when creating a class, sometimes there will be multiple instances, so how is the constructor called?

PHP's constructor call searches upwards from itself and executes the most recent one to make the call.