how to search by skipping equidistant letters

[gilgalbiblewhee]

U can try something like this?

<?php
$string = "xxxlxxxoxxxvxxxexxx";
$result = (string)NULL;
$done = false;

$string = substr($string,3);
$split = str_split($string);
$result .= $split[0];
while(!$done) {

    $string = substr($string,4);
    $split = str_split($string);
    $result .= $split[0];
    
    if(empty($string))
        $done = true;
}
echo $result;
?>

Let me rephrase this. So you set the number to 3 so that it would search the string at the skip of 3 letters.
What I'm looking for is that I want to search a $keyword like love within the string.

1. My logic is that I have to break the string into an array of letters;
2. break the $keyword into and array of letters
3. create a for loop to search
4. make the array of the count($keyword)*$i not exceed the count($string) else exit the loop
5. here's where I find tricky: I need to match all the letters of the keyword to the letters of the string at the given equidistant letter sequence or $els which is a variable, or maybe use the $i from the for loop instead.

I have a question about the if statement:
can i bring in an array within the if brackets:

if($kw[$k]==$str[$i] && $kw[$k]==$str[$i]...depending at the number of $key){
...}