PHP magic function __call() usage_PHP tutorial-PHP Tutorial-php.cn

PHP magic function __call() usage_PHP tutorial

WBOY

Release： 2016-07-13 17:13:03

Original

844 people have browsed it

The so-called magic function of PHP, simply put, is a method that has a specific name in PHP - all starting with two underscores, and the PHP interpreter will automatically find and run the method when it reaches a certain time. The most common magic function is of course the constructor method: __construct.

Method calling in PHP works like this. First, the PHP interpreter looks for methods on the class. If the method exists, PHP calls it. If not, then the magic function __call on the class is called (if this method exists). If __call fails, the parent class method is called, and so on.

It seems a bit too perverted to say this with red lips and white teeth. Let’s give an example. Look at the following code:

The code is as follows

Copy code

代码如下	复制代码
class test{ public function __construct(){ echo "this is construct!n"; } } ……

class test{

public function __construct(){

echo "this is construct!n";

}

代码如下	复制代码
$send = new test(); $send-> atomBomb();

…

In this test class test, there is only one constructor that outputs some dispensable garbage characters, and nothing else;

At this time, we instantiate it and call a * method. What do you think it will do? We do this right away and watch:

The code is as follows

Copy code

代码如下

复制代码

……
class test{
public function __construct(){
echo "this is construct!n";
}

public function __call($name,$arg){
echo “function name:”,$name,”n arg:”.$arg;
}
}
……

重复上边的调用方式：
$send = new test();
$send-> atomBomb(‘ab’,9);

$send = new test();

$send-> atomBomb();

The result is conceivable, he will definitely tell you that there is no such method - we indeed do not have such a * method! The error message is as follows:

Debug Error: test.php line 9 – Call to undefined method test::atomBomb()

Then let’s modify this class and add a __call method to see what happens:

代码如下	复制代码
function name:atomBomb arg:Array

The code is as follows	Copy code
…… class test{ public function __construct(){ echo "this is construct!n"; } public function __call($name,$arg){ echo “function name:”,$name,”n arg:”.$arg; } } … Repeat the above calling method: $send = new test(); $send-> atomBomb(‘ab’,9);

The results you see this time are definitely different from last time. The results are as follows: this is construct! //This is output by the constructor itself //The following are the outputs of the __call function

The code is as follows	Copy code
function name:atomBomb arg:Array

And we can easily see that __call has two parameters. The first parameter: the name of the method to be called, and the second parameter: the parameters entered when calling the method (this place is an array).

I don’t know if you understand this much. I think if you do, you will definitely ask what is the use of this thing? What can we use it for?

Then let me give you an idea of how to use it - apply what you have learned! Just imagine, if you treat all tables in a database as objects and perform CURD operations on them, how many classes do you need to write? Of course, if your array library only has two tables, you can tell me that there are only two classes! But what if there are 108 tables (for example, dede has 108 tables), and 108 classes are entered manually? Obviously unscientific, what is the most expensive thing in the 21st century? --time!

We can definitely write a class, and the rest will be created automatically. I found a piece of code in IBM and simplified it. You can take a look. This is something written by a senior engineer.

代码如下

复制代码

class DBObject{
private $id = 0;
private $table;
private $fields = array();
function __construct( $table, $fields ) {
$this->table = $table;
foreach( $fields as $key )
$this->fields[ $key ] = null;
}
function __call( $method, $args ) {
if ( preg_match( "/set_(.*)/", $method, $found ) ) {
if ( array_key_exists( $found[1], $this->fields ) ) {
$this->fields[ $found[1] ] = $args[0];
return true;
}
}
else if ( preg_match( "/get_(.*)/", $method, $found ) ) {
if ( array_key_exists( $found[1], $this->fields ) ) {
return $this->fields[ $found[1] ];
}
}
return false;
}
function insert() {
global $db;
$fields = $this->table."_id, ";
$fields .= join( ", ", array_keys( $this->fields ) );
$inspoints = array( "0" );
foreach( array_keys( $this->fields ) as $field )
$inspoints []= "?";
$inspt = join( ", ", $inspoints );
$sql = "INSERT INTO ".$this->table." ( $fields ) VALUES ( $inspt )";
$values = array();
foreach( array_keys( $this->fields ) as $field )
$values []= $this->fields[ $field ];
$sth = $db->prepare( $sql );
$db->execute( $sth, $values );
$res = $db->query( "SELECT last_insert_id()" );
$res->fetchInto( $row );
$this->id = $row[0];
return $row[0];
}

//下边删除了3个方法分别是更新update，删除一个，删除全部（战地注）
}
$book = new DBObject( 'book', array( 'author',
'title', 'publisher' ) );
$book->delete_all();
$book->set_title( "PHP Hacks" );
$book->set_author( "Jack Herrington" );
$book->set_publisher( "O'Reilly" );
$id = $book->insert();
echo ( "New book id = $idn" );
$book->set_title( "Podcasting Hacks" );
$book->update();
$book2 = new DBObject( 'book', array( 'author',
'title', 'publisher' ) );
$book2->load( $id );
echo( "Title = ".$book2->get_title()."n" );
$book2->delete( );……