Explanation of the internal execution process of the PHP iterator

Copy codeThe Code is as follows:
Class myIterator implements Iterator {
Private $ position = 0;
Private $ array = array (
"First_element ",
"Second_element ",
"Last_element ",
);

Public function _ construct (){
$ This-> position = 0;
}

Function rewind (){
Var_dump (_ METHOD __);
$ This-> position = 0;
}

Function current (){
Var_dump (_ METHOD __);
Return $ this-> array [$ this-> position];
}

Function key (){
Var_dump (_ METHOD __);
Return $ this-> position;
}

Function next (){
Var_dump (_ METHOD __);
++ $ This-> position;
}

Function valid (){
Var_dump (_ METHOD __);
Return isset ($ this-> array [$ this-> position]);
}
}

$ It = new myIterator;

Foreach ($ it as $ key => $ value ){
Echo 'output key value :';
Var_dump ($ key, $ value );
// Echo $ key;
Echo "\ n ";
}

Program running output:
Copy codeThe Code is as follows:
String (18) "myIterator: rewind"
String (17) "myIterator: valid"
String (19) "myIterator: current"
String (15) "myIterator: key"
Output key value: int (0)
String (13) "first_element"

String (16) "myIterator: next"
String (17) "myIterator: valid"
String (19) "myIterator: current"
String (15) "myIterator: key"
Output key value: int (1)
String (14) "second_element"

String (16) "myIterator: next"
String (17) "myIterator: valid"
String (19) "myIterator: current"
String (15) "myIterator: key"
Output key value: int (2)
String (12) "last_element"

String (16) "myIterator: next"
String (17) "myIterator: valid"

The following method is required for an iterator:
Iterator: current-Return the current element returns the current element
Iterator: key-Return the key of the current element returns the key of the current element
Iterator: next-Move forward to next element Move to the next element
Iterator: rewind-Rewind the Iterator to the first element to return to the first element
Iterator: valid-Checks if current position is valid check validity of the current position
If you are not clear about the content workflow of the iterator, you can view the traversal process of the array by the iterator below:
Copy codeThe Code is as follows:
/**
* @ Author concise modern magic http://www.nowamagic.net
*/
Class MyIterator implements Iterator
{
Private $ var = array ();

Public function _ construct ($ array)
{
If (is_array ($ array )){
$ This-> var = $ array;
}
}

Public function rewind (){
Echo "returns the first element \ n ";
Reset ($ this-> var );
}

Public function current (){
$ Var = current ($ this-> var );
Echo "Current element: $ var \ n ";
Return $ var;
}

Public function key (){
$ Var = key ($ this-> var );
Echo "Key of the current element: $ var \ n ";
Return $ var;
}

Public function next (){
$ Var = next ($ this-> var );
Echo "Move to the next element: $ var \ n ";
Return $ var;
}

Public function valid (){
$ Var = $ this-> current ()! = False;
Echo "check validity: {$ var} \ n ";
Return $ var;
}
}

$ Values = array (1, 2, 3 );
$ It = new MyIterator ($ values );

Foreach ($ it as $ k => $ v ){
Print "key-value pair -- key $ k: value $ v \ n ";
}

Program running result:
Copy codeThe Code is as follows:
Returns the first element.
Current element: 1
Check validity: 1
Current element: 1
Key of the current element: 0
Key-value pair -- key 0: value 1

Move to the next element: 2
Current element: 2
Check validity: 1
Current element: 2
Key of the current element: 1
Key-value pair -- key 1: value 2

Move to the next element: 3
Current element: 3
Check validity: 1
Current element: 3
Key of the current element: 2
Key-value pair -- key 2: value 3

Move to the next element:
Current element:
Check validity:

Is it clear now?