Can't access value of protected static variable php 7.0.13 - php

Question

I'm trying to implement a DataTable class in php which will be basically a table to contain data just like an sql table and will be made of array()
The class is defined as followed:
class DataTable{
protected static $tabela; // table
//columns and strips, each column point to a strip
public function __construct($colunas, $faixas) {
$this->tabela = array();
$this->constroiDt($colunas, $faixas); //builds the table
}
public function getRows($where){
// todo
}
public static function getTabela(){
return $this->tabela;
}
private function constroiDt($colunas, $faixas){
if(count($colunas)!= count($faixas)){
$this->tabela = null;
return;
}
$i=0;
foreach($colunas as $cl){
$this->tabela = array_merge($this->tabela, array($cl => $faixas[$i]));
$i += $i + 1;
}
// the result will be an array like ('col1' => ('val1','val2'), 'col2' => ('val1','val2'))
// if I want to access a value, just type array['col1'][0] for example
}
}
Outside of the class function, when I create an example DT and try to access it, it seems that will work:
$columns = array("name", "age");
$strips = array(array("someone","another person"),array("20","30"));
$dt1 = new DataTable($columns, $strips);
var_dump($dt1); // will print:
// object(DataTable)#1 (1) { ["tabela"]=> array(2) { ["nome"]=> array(2) { [0]=> string(6) "fulano" [1]=> string(7) "ciclano" } ["idade"]=> array(2) { [0]=> string(2) "20" [1]=> string(2) "30" } } }
But then I add echo "--- " . $dt1::getTabela()['nome'][0];
It doesn't even print the ---. var_dump($dt1::getTabela()) and var_dump($dt1->getTabela()) also is blank. What is being missed here? Tried also this but didn't work.

Answer 1

You shouldn't use $this in a static function / for static properties as there is not necessarily an object context to use.
Instead, you should use self::$tabela everywhere instead.
Or change your variable (and the related methods...) to a "normal" protected property:
protected $tabela;

Answer 2

You are mixing static variables with non static accesors
i just put your code and i got a lot of errors/notices
NOTICE Accessing static property DataTable::$tabela as non static on line number 10
NOTICE Accessing static property DataTable::$tabela as non static on line number 31
NOTICE Accessing static property DataTable::$tabela as non static on line number 31
NOTICE Accessing static property DataTable::$tabela as non static on line number 31
NOTICE Accessing static property DataTable::$tabela as non static on line number 31
object(DataTable)#1 (1) { ["tabela"]=> array(2) { ["name"]=> array(2) { [0]=> string(7) "someone" [1]=> string(14) "another person" } ["age"]=> array(2) { [0]=> string(2) "20" [1]=> string(2) "30" } } }
FATAL ERROR Uncaught Error: Using $this when not in object context in /home/phptest/public_html/code.php70(5) : eval()'d code:20 Stack trace: #0 /home/phptest/public_html/code.php70(5) : eval()'d code(44): DataTable::getTabela() #1 /home/phptest/public_html/code.php70(5): eval() #2 {main} thrown on line number 20