arrays - How to check if a String is not empty in php, to prevent undefined function calls?

one text

Solution:

if (preg_match('/SA(?!P)|Schulaufgabe|Unterrichtsende/',$array[$i][$k])) {
    echo "<td style='color: red'>" . $array[$i][$k];          
}

The Answer was in the method .includes() which just partly worked, I do not recommend using it! Even though I found it somewhere in the phpManual