我在学校学习PHP，每个人都有这个不工作

We use MAMP for our servers and html/css/php files. I have double checked everything and im SURE this has no errors really. It ends up with a local host error. which means it won't display my work. Here is my work:

-- main.php --

<?php

require 'person.php'

$person = new Person;
$person->name = 'Froggy';
$person->age = '15';

echo $person->sentence();

 ?>

--- person.php ---

<?php
class Person {
  public $name;
  public $age;


  public function sentence() {
  return $this->name . 'is' . '$this->age' . ' years old';
  }
}
?>

So this simple code would show me "'Froggy' is '15' years old" but it wont work. Help?

Parse error:

Add semi-colon here

require 'person.php';

Again, change function to:

public function sentence() {
 return $this->name . ' is ' . $this->age . ' years old';
}

Issue was that $this->age was having single quote around it.

Variables inside single quotes are not parsed, it is called variable interpolation.

Variables inside double quotes however, can be parsed.

Output:

Froggy is 15 years old

Remove the quotes around $this->age:

<?php
class Person {
  public $name;
  public $age;


  public function sentence() {
  return $this->name . 'is' . $this->age . ' years old';
  }
}

If you want the quotes in your output, you can return this in your function:

return "'$this->name' is '$this->age' years old";