Question

I’m writing a blacklist word checker. I’ve named the script as blacklist_check.php and it looks like this:

<?php
$black_list = [
  'ass',
  'anus',
  /* many others that i skipped here */
];

function is_black_listed ($word) {
  return in_array($word, $black_list);
}
?>

However when I use the is_black_listed function, I always get Warning: in_array() expects parameter 2 to be array, null given.

Should I put the $black_list array inside of is_black_listed function? I don’t want to do it, as the array would always get created when I call the function, instead of it being just one time when I require (or include) the script!

Should I use global $black_list inside of is_black_listed function?

Help me out with the best practice to solve this problem!

Answer 1

Don’t use a global variable, they’re pretty hard to maintain and make your code less readable. Instead, just pass the array to the function:

function is_black_listed ($word, $black_list)

Then call it with:

is_black_listed( "bad words!", $black_list);

Better yet, create a class to do this, and create the array as a member variable:

class WordFilter {
    private $black_list = [ ... ];

    function __construct( $words = array()) {
        // Optionally add dynamic words to the list
        foreach( $words as $word) 
            $black_list[] = $word;
    }

    function is_black_listed( $word) {
        return in_array( $word, $this->black_list);
    }
}

$filter = new WordFilter( array( 'potty', 'mouth'));
$filter->is_black_listed( "bad");