Reduce whole text to some words in PHP - php

Question

I have a problem. I need a "text reducer".
What i mean: I wrote to text area any words, for example: John Doe is good boy; Then i press some button, and it will get something like:
John Doe
So, it will only output defined worlds, like John Doe, or milk or something like that
Thanks for your help

Answer 1

If you know a black list of words you want to strip out, you could use the array replace function: str_replace:
http://php.net/manual/en/function.str-replace.php
like this:
$blacklist = ['ugly', 'bad', 'censored'];
$yourString = str_replace($yourString, $blacklist, '');
This will remove every word in your blacklist, from your input string.
If you need a whitelist based filter, you could use split your string into an array of words, and then use the array_filter function:
http://php.net/manual/en/function.preg-split.php
http://php.net/manual/en/function.array-filter.php
using something similar to:
$whitelist = ['good', 'neat', 'stuff'];
$tokens = preg_split("/[\s,]+/", $yourString);
$filtered = array_filter($tokens, function ($item) {
return in_array($token, $whitelist);
});
$finalString = implode(' ', $filtered);

Answer 2

Yes you can write a function in this case it receives an array as parameter, but if is static, you could save it on the function.
Also, this could work using a regex with preg_match, but i'll leave that for you.
Currently ignores case thanks to `strtolower', if you don't want to ignore the case, remove this function calls.
function printWhiteListedText($arrWhitelist, $str){
$auxStr = "";
foreach($arrWhitelist as $word){
if(strpos(strtolower($str), strtolower($word)) > -1){
$auxStr .= $word . ' ';
}
}
return trim($auxStr);
}
echo printWhiteListedText(['Hello', 'world'], 'hello this world is great');