String Searching Algorithms in PHP

<?php
class KMPAlgorithm {
    public static function kmpSearch($text, $pattern) {
        $lps = self::computeLPSArray($pattern);
        $i = 0; // index for text
        $j = 0; // index for pattern
        $textLength = strlen($text);
        $patternLength = strlen($pattern);
        
        while ($i < $textLength) {
            if ($pattern[$j] === $text[$i]) {
                $i++;
                $j++;
            }
            if ($j == $patternLength) {
                return $i - $j;
            } elseif ($i < $textLength && $pattern[$j] !== $text[$i]) {
                if ($j != 0) {
                    $j = $lps[$j - 1];
                } else {
                    $i++;
                }
            }
        }
        return -1;
    }

    private static function computeLPSArray($pattern) {
        $length = 0;
        $i = 1;
        $patternLength = strlen($pattern);
        $lps = array_fill(0, $patternLength, 0);
        $lps[0] = 0; // lps[0] is always 0

        while ($i < $patternLength) {
            if ($pattern[$i] === $pattern[$length]) {
                $length++;
                $lps[$i] = $length;
                $i++;
            } else {
                if ($length != 0) {
                    $length = $lps[$length - 1];
                } else {
                    $lps[$i] = 0;
                    $i++;
                }
            }
        }
        return $lps;
    }
}

// Example usage
$text = "abxabcabcaby";
$pattern = "abcaby";
$result = KMPAlgorithm::kmpSearch($text, $pattern);
echo $result;  // Output: 6
?>