PHP Only allow specific words in a string [closed]

I’m trying to check if the given string contains words that are not listen in my $allowed array. If it does I want them replaced with “”.

So let’s say my string contains “Hello World” and “World” is not in my allowed words it should replace “World” with “”.

Another issue I have is that my current implementation is case sensitive.

$string = "Test new world";
$allowed = array('hello', 'test');
if(in_array($string, $allowed)) {
     
}
else {
    // Return false or Replace with ""
}

Answer

I can answer partially by showing you how to keep word boundaried words, removing everything else from the string:

<?php

$input  = 'hotdogs are food, not actual HOT dogs.  The latter being dog animals that are hot.';

$words = 
[
    'hot',
    'dog'
];
$regex  = '@b(' . implode($words, '|') . ')b@i';
$output = '';
if(preg_match_all($regex, $input, $matches))
    $output = implode($matches[0]);

print $output;

Output:

HOTdoghot