Simple PHP class - php

Question

I am learning php and created the below class, but I can't seem to figure out why it giving me the below errors which says:
144
Warning: Missing argument 1 for setters::set_a(), called in C:\xampp\htdocs\php\accessmod2.php on line 19 and defined in C:\xampp\htdocs\php\accessmod2.php on line 9
Notice: Undefined variable: value in C:\xampp\htdocs\php\accessmod2.php on line 11
<?php
class setters{
private $a = 144;
public function get_a(){
return $this->a;
}
public function set_a($value){
$this->a = $value;
}
}
$example = new setters();
echo $example->get_a()."<br />";
$example->set_a(15)."<br />";
echo $example->set_a()."<br />";
?>

Answer 1

You have to use a parameter for the set() function. But in your case, I think you just want to see if the set() function have work. So use the get() function.
So change to this :
echo $example->get_a()."<br />";
$example->set_a(15)."<br />";
echo $example->get_a()."<br />";
And the result is :
144
15

Answer 2

Check your last line:
echo $example->set_a()."<br />";
set_a() requires a parameter but it is empty. If you change it like this, it will work:
echo $example->set_a('someparameterhere')."<br />";

Answer 3

Your second call to ->set_a requires a parameter :
<?php
class setters{
private $a = 144;
public function get_a(){
return $this->a;
}
public function set_a($value){
$this->a = $value;
}
}
$example = new setters();
echo $example->get_a()."<br />";
$example->set_a(15)."<br />";
$example->set_a(23)."<br />"; // ◄■■■ PARAMETER FOR "SET_A".
?>
You can also use an "optional" parameter :
<?php
class setters{
private $a = 144;
public function get_a(){
return $this->a;
}
public function set_a( $value = -1 ){ // ◄■■■ OPTIONAL PARAMETER.
$this->a = $value;
}
}
$example = new setters();
echo $example->get_a()."<br />";
$example->set_a()."<br />"; // ◄■■■ OPTIONAL PARAMETER ($a = -1).
echo $example->get_a()."<br />"; // ◄■■■ NEW VALUE = -1.
?>

Answer 4

You are calling set_a twice.
After set, you need call get_a to show the value.
echo $example->get_a()."<br />";
$example->set_a(15)."<br />";
echo $example->get_a()."<br />";