regex - count how many times this "ABD" shows in my document using PHP -

<?php    $file = fopen("verylongword.txt", "r");    /*   inside verylongword.txt   abdbbaabaadbbadabdaddaabbabdabdbbaabaadbbadabdaddaabbabdabdbbaabaadbbadabdaddaabbabdabdbbaabaadbbadabdaddaabbabdabdbbaabaadbbadabdaddaabbabd   abdbbaabaadbbadabdaddaabbabdabdbbaabaadbbadabdaddaabbabdabdbbaabaadbbadabdaddaabbabdabdbbaabaadbbadabdaddaabbabdabdbbaabaadbbadabdaddaabbabd       */    $word = "";   while(!feof($file)) {     $line = fgets($file);     $word .= trim($line);   }   fclose($file);    $subseq = null;    $count = 0;    // how  write code count number of instances of subsequence in word string   // want count how many   abd in verylongword.txt    print $subseq . " shows " . $count . " times <br/>";  ?> 

there's function that: substr_count

$contentsofverylongword = file_get_contents("verylongword.txt"); $count = substr_count($contentsofverylongword, 'abd');