php中带有参数问题的构造函数

I'm not able to get the arguments passed onto a function in the constructor. Let me a bit clear with the code snippet below.

class Foo{
    public function __construct($arg){
         $arg = $arg1;
    }

    public function A($arg1){
        echo $arg1;
    }
}

$obj = new Foo();
$data = $obj->A('hello');

Here, the call is being made to the function A with an argument. I'm not able to get the same argument value in the constructor. I'm just giving an idea of my code.

• Check your variable names! Do not attach numbers. Give them proper individual names to avoid errors.
• Read a bit on Constructors in the manual: http://php.net/manual/en/language.oop5.decon.php

Some additional examples:

Constructor Argument

class Foo{
    public function __construct($argument){
        echo $argument;
    }
}

new Foo('Hello World');

Constructor Argument + Set argument to object as property

class Foo
{
    public $argument = '';     

    public function __construct($argument){
        $this->argument = $argument;
    }

    public function printIt()
    {
        echo $this->argument;
    }
}

$foo = new Foo('Hello World');
$foo->printIt();

In your _construct, $arg1 is not available for use, since it doesn't come from anywhere. This code would work fine if you would just remove $arg = $arg1; and remove $arg from the parameters of your constructor.

Right now the constructor is trying to pass a value from a variable that doesn't exist on that scope to $arg.

<?php

class Foo {

    private $arg1;

    public function __construct($arg) {
        $this->arg1 = $arg;
    }

    public function A() {
        echo $this->arg1;
    }

}

$obj = new Foo("hello");
$data = $obj->A();

try this, it will work