how to search by skipping equidistant letters

[gilgalbiblewhee]

I want to search word within a string by equidistant letters pattern:
Example I want to search love within the x's at a skip of 3 letters or every 4th letter:

xxxlxxxoxxxvxxxexxx

My logic is that first I need to explode the keyword:

str_split($keyword);

But I'm not sure afterward. But it's not splitting the into hebrew letters, rather a black diamond shape with a ?.
So far I have this:

<?php
for($tdid=0; $tdid < count($id); $tdid++){
    $strText=stripslashes(mysql_escape_string($textData[$tdid]));
    include("../includefiles/vowelmarks.php");
    for($i=0; $i<count($vm); $i++){
        //echo $vm[$i];
        $strText=str_replace($vm[$i], "", $strText);
    }
    $letters=str_split($strText);
    for($i=0; $i<count($letters); $i++){
        if($letters[$i]!==" "){
            if($i==0 or ($i&#37;2)==22){
?><tr><?php
            }
            //include("../includefiles/highlight_getBibleCode.php");
            echo "<td id=\"regular[]\" style=\"font-size: 14px; direction: rtl; font-family:'SBL Hebrew';\">".$letters[$i]."</td>\n";
            if(($i%2)==22){
?></tr><?php
            }
        }
    }
}