Regex for getting strings that contains only the words from the pattern list?

Question

Consider the following array elements

 1.benclinton
 2.clintonharry
 3.harryben
 4.benwill
 5.jasonsmith
 6.smithclinton

Assume the pattern list is ben,harry,clinton, then the result I should get is

1.benclinton  
2.clintonharry  
3.harryben

So,essentially the result should contain strings that contains only the words that are in the pattern list. Order is not important

Also, each strings will not be having more than two words. i.e. bensmithwill will never be a case.

Since all my strings are in an array, I thought of using preg_grep in php to do this but i am struck in framing correct regex for this.

what regex can achieve this? Is there any other efficient way apart from regex matching that will do the work?

Thanks in advance!

ArtisticPhoenix · Accepted Answer · 2019-03-10T04:45:20.850

3

Something like this

$names_list = ['benclinton','clintonharry','harryben','benwill','jasonsmith','smithclinton'];
$names = ['ben','harry','clinton'];  

$matches = preg_grep('/('.implode('|',$names).')(?1)/', $names_list);
//-  /(ben|harry|clinton)(?1)/  -- (?1) = recurse capture group 1 

print_r($matches);

Output

Array
(
    [0] => benclinton
    [1] => clintonharry
    [2] => harryben
)

Sandbox

This requires that at least two of the names (even the same one 2x) match. But that is kind of a given in this case or everything would match.

If you want to be extra careful, if the $names can contain something important to regex, such as +,*, \ etc. you can add this

$matches = preg_grep('/('.implode('|',array_map(function($name){return preg_quote($name,'/');},$names)).')(?1)/', $names_list);

edited Mar 10 '19 at 04:45

answered Mar 10 '19 at 04:36

ArtisticPhoenix

21,464
2
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38

This matches `benbenclinton`. Not sure if the OP expects that a term be an exact match of two substrings. – Tim Biegeleisen Mar 10 '19 at 04:46
@TimBiegeleisen - as does yours. [Sandbox](http://sandbox.onlinephpfunctions.com/code/08f48602f1d5d7a3bf2b439f3d43c4480a9b0608) – ArtisticPhoenix Mar 10 '19 at 04:48
I can do the same thing with `^` and `$` [Sandbox](http://sandbox.onlinephpfunctions.com/code/d93bd7b6cc628d0519d077e0ce55019b92415d04) - just saying. :-) – ArtisticPhoenix Mar 10 '19 at 04:50

Tim Biegeleisen · Answer 2 · 2019-03-10T04:48:50.820

It appears that you want to match array elements which are exact combinations of two keywords. For a regex approach, we can try taking the cross product of the vector of keyords, and then generate an alternation. Then, we can use preg_grep against your input array to find all matching elements.

$array = array("benclinton", "clintonharry", "harryben", "benwill", "jasonsmith", "smithclinton");
$input = array("ben", "harry", "clinton");
$regex = "";
foreach ($input as $term1)  {
    foreach ($input as $term2)  {
        if ($regex != "") $regex .= "|";
        $regex .= $term1.$term2;
    }
}
$regex = "/^(" . $regex . ")$/";
$matches = preg_grep($regex, $array);
print_r($matches);

Array
(
    [0] => benclinton
    [1] => clintonharry
    [2] => harryben
)

Here is the regex alternation generated by the above script:

(benben|benharry|benclinton|harryben|harryharry|harryclinton|clintonben|
    clintonharry|clintonclinton)

Thanks. Is there any way without using for loop? – Mohamed Abdullah Mar 10 '19 at 04:36 — Mohamed Abdullah, Mar 10 '19 at 04:36

prasanth · Answer 3 · 2019-03-10T04:50:18.420

Without Regex.Do with array_filter and strpos

Filter array with respected matching second array the count greater then 1

Sandbox

<?php
$a = ['benclinton','clintonharry','harryben','benwill','jasonsmith','smithclinton'];
$a2 = ['ben','clinton','harry'];
$res = array_filter($a,function($str="") use($a2){
    $r =array_filter($a2,function($a2str) use($str){
        return strpos($str,$a2str) !== FALSE;
    });
    return count($r) > 1;
});
print_r($res);
?>

Regex for getting strings that contains only the words from the pattern list?

3 Answers3