php remove duplicates from string, if duplicate length is > 4 - php

Question

I want to remove duplicates, if these duplicates got a length of more then 4 characters.
How can we achieve that? My current code also remove the duplicate - values.
CODE:
$seoproducttitle = 'HP Chromebook Chromebook 11 G5 EE - 11.6 inch - Intel® Celeron® - 4LT18EA#ABH';
$productnamestring = $seoproducttitle;
$findseo = array('/\h+inch (?:(i[357])-\w+|\h+\w+)?/', '/(\w+)#\w+/');
$replaceseo = array('" $1', '$1');
$productnamingseo = preg_replace($findseo, $replaceseo, $productnamestring);
echo implode(' ', array_unique(explode(' ', $productnamingseo)));
This outputs: HP Chromebook 11 G5 EE - 11.6" Intel® Celeron® 4LT18EA
It should output: HP Chromebook 11 G5 EE - 11.6" - Intel® Celeron® - 4LT18EA
Or: Apple MacBook Air MacBook Air - 13.3 inch - Intel Core i5-8e - MRE82N/A
Should be: Apple MacBook Air - 13.3 inch - Intel Core i5-8e - MRE82N/A
EXAMPLE: http://sandbox.onlinephpfunctions.com/code/5bcaaf47ca97d6dee359802f2d71c2d889c0d091

Answer 1

Update
Based on comments from OP, the required regex is
/(^| )(.{4,}) (.*)\2/
This looks for a group of 4 or more characters preceded by either a space or the start of the line and followed by a space, some number of other characters and then the group repeated again. The regex is replaced by $1$2 $3 which effectively removes the duplicate string. A couple of examples:
$seoproducttitle = 'Apple MacBook Air MacBook Air - 13.3 inch - Intel Core i5-8e - MRE82N/A';
echo preg_replace('/(^| )(.{4,}) (.*)\2/', "$1$2 $3", $seoproducttitle) . "\n";
$seoproducttitle = 'HP Chromebook 11 G5 EE Chromebook - 11.6 inch - Intel® Intel® Celeron® - 4LT18EA#ABH 4LT18EA#ABH';
echo preg_replace('/(^| )(.{4,}) (.*)\2/', "$1$2 $3", $seoproducttitle) . "\n";
Output:
Apple MacBook Air - 13.3 inch - Intel Core i5-8e - MRE82N/A Array
HP Chromebook 11 G5 EE - 11.6 inch - Intel® Celeron® - 4LT18EA#ABH
Updated demo on 3v4l.org
Original Answer
You could use this regex:
\b([^ ]{4,})( |$)(.*)\1
It looks for a group of 4 or more non-blank characters, followed by a space or end-of-string, followed by some number of other characters and then the first group repeated. The regex is replaced by $1$3 which effectively removes the duplicate string. e.g.
$seoproducttitle = 'HP Chromebook 11 G5 EE Chromebook - 11.6 inch - Intel® Intel® Celeron® - 4LT18EA#ABH 4LT18EA#ABH';
echo preg_replace('/\b([^ ]{4,})( |$)(.*)\1/', "$1$3", $seoproducttitle);
Output:
HP Chromebook11 G5 EE - 11.6 inch - Intel® Celeron® - 4LT18EA#ABH
Demo on 3v4l.org

Answer 2

Computers only do what we tell them, so you first need to explain the process to yourself in plain language. Then translate that to code. Then if you're having trouble doing that you've at least got a proper description of the problem to post on StackOverflow .
$words = explode(' ', $productnamingseo);
// start with an empty list of words we've seen
$output = [];
// for every word
foreach($words as $word) {
// if it's longer than 4 chars and we've already seen it
if( mb_strlen($word) >= 4 && in_array($word, $output) ) {
// debug: show omitted words
// $output[] = str_repeat('X', mb_strlen($word));
// skip it
continue;
}
// otherwise, add it to the list of words we've already seen
$output[] = $word;
}
var_dump(
$productnamingseo,
implode(' ', $output)
);