How to cache Methods for one process? - php

Question

I'm trying to cache an Object's method, so every time I call the Class and the method, it won't process again after first time.
Here is what I'm trying to achieve,
class App {
public $data = null;
public function print() {
if ( $this->data === null ) {
$this->data = "First time.";
}
else {
$this->data = "After first time.";
}
return $this->data;
}
}
$data = new App();
echo $data->print() . "<br>";
echo $data->print() . "<br>";
$data2 = new App();
echo $data2->print() . "<br>";
echo $data2->print() . "<br>";
Result
First time.
After first time.
First time.
After first time.
As you can see, it's processing the print() method again when I call it again in $data2.
Is it possible to cache so result will be
First time.
After first time.
After first time.
After first time.

Answer 1

For get your required constant output you need to
change the public variable inside the class to as static variable
Because public static variables share all the available instances of that class each time.
class App {
public static $data = null;
public function print() {
if ( self::$data === null ) {
self::$data = "First time.";
}
else {
self::$data = "After first time.";
}
return self::$data;
}
}
$data = new App();
echo $data->print() . "<br>";
echo $data->print() . "<br>";
$data2 = new App();
echo $data2->print() . "<br>";
echo $data2->print() . "<br>";
Result will be :
First time.
After first time.
After first time.
After first time.