Error handler function in application - php

Question

I'm relatively new in programming. I'm trying to catch and display errors in my aplication. With global variable is simple:
$errors = '';
class Name {
/**
* Validate form
*/
public function validate_form() {
global $errors;
(...)
if ( empty($_POST["blabla"]) ) {
$errors = 'Error';
}
(...)
return;
}
/**
* Display errors
*/
public function show_error() {
global $errors;
if(!empty($errors)) return '<div class="error">' . PHP_EOL . htmlspecialchars($errors) .'</div>';
}
}
...but i read that you should not use global variables. How can i do the same thing without global variable?
Sorry for my english ;)

Answer 1

How about not making it global, ie:
<?php
class Name {
public $errors;
/*
* Validate form
*/
public function validate_form() {
(...)
if ( empty($_POST["blabla"]) ) {
$this->errors = 'Error';
}
(...)
return;
}
}
Then everytime you run a fucntion in that class, check if an error was generated:
$obj = new Name()->validate_form();
if(isset($obj->errors)){
//oops, an error occured, do something
}

Answer 2

You can throw Exceptions
<?php
class Name {
/**
* Validate form
*/
public function validate_form() {
(...)
if ( empty($_POST["blabla"]) ) {
throw new RuntimeException( 'Error' );
}
(...)
return;
}
$obj = new Name();
/**
* Display errors
*/
public function show_error($e) {
return '<div class="error">' . PHP_EOL . htmlspecialchars($e->getMessage()) .'</div>';
}
}
// TEST
try {
$obj->validate_form();
}
catch(Exception $e) {
$obj->show_error($e);
}