PHP Using the array_filter - php

Question

I will try to explain my situation as best as possible so bear with me.
I have an array with single words in them, for example:
This
is
a
test
array
Now i created another array that looks alike but with 2 words, which looks like this:
This is
is a
a test
test array
Ok here is where my problem starts. I have an array of 'common words' those words should be exluded from the array. Let's say those common words would be is and a for this example. Right now i search for common words first on the single word array so i can use if(in_array($word, $common_words)) continue; Which makes it skip the one if it's in the common_words array.
But this would result in this array:
This test
test array
But this is not how i want it to happen. It should be like this:
test array
Because this is the only 1 that had these 2 words next to eachother originally before we started to take out the 'common_words'. (are you still with me?)
The problem here is that if(in_array) doesn't work anymore if I have an array with 2 words. So i did some research and stumbled upon the array_filter command. I think this is what I need but i'm at a total loss as on how to use/apply it to my code.
I hope I explained it well enough for you to understand what my problem is and I would appreciate it if someone could help me.
Thanks in advance!

Answer 1

Your guess is correct, you can use:
$array = ['this is', 'array array', 'an array', 'test array'];
$stop = ['is', 'test'];
$array = array_filter($array, function($x) use ($stop)
{
return !preg_match('/('.join(')|(', $stop).')/', $x);
});
-i.e. exclude all items with certain words in it by pattern using array_filter()
This will work with filtering because it will match by regex, i.e. from $stop we'll get regex (is)|(test)
A good idea will be to evaluate regex separately so do not evaluate it each time inside array_filter() iteration, like:
$array = ['this is', 'array array', 'an array', 'test array'];
$stop = ['is', 'test'];
$pattern = '/('.join(')|(', $stop).')/';
$array = array_filter($array, function($x) use ($pattern)
{
return !preg_match($pattern, $x);
});
Important note#1: if your stop words may contain some special characters that will be treated in regex in special way, it's needed to use preg_quote() like:
$pattern = '/'.join('|', array_map(function($x)
{
return '('.preg_quote($x, '/').')';
}, $stop)).'/';
$array = array_filter($array, function($x) use ($pattern)
{
return !preg_match($pattern, $x);
});
Important note#2: If your array of stopwords is too long this may cause regex compilation fail because of it's length (too large). There are some tricks to overcome it, but if it's your case, you'd better to use strpos() instead:
$array = array_filter($array, function($x) use ($stop)
{
foreach($stop as $word)
{
if(false!==strpos($x, $word))
{
return false;
}
}
return true;
});

Answer 2

I think, the bes way, two operators: array_diff and array_unique
$a[] = 'This';
$a[] = 'is';
$a[] = 'is';
$a[] = 'a';
$a[] = 'a';
$a[] = 'test';
$a[] = 'test';
$a[] = 'array';
$excluded = array('is', 'a');
$result = array_diff($a, $excluded); // Remove all excluded words
$result = array_unique($result); // unique values
var_dump($result);
And result:
array (size=3)
0 => string 'This' (length=4)
5 => string 'test' (length=4)
7 => string 'array' (length=5)