remove wordpress generated custom image sizes

<?php

$dir    = './';
$files1 = scandir($dir);

foreach (glob("*.jpg") as $file) {
    echo $file;

    $newFile = $file;
    $searchWord = array('25x25', '1280x', '100x100', '150x150', '300x240','300x', '600x', '768x', '900x', '1024x','1820x', '854x', '400x', '477x', '480x','672x', '960x', '750x');

    if (preg_match('/' . implode('|', $searchWord) . '/', $newFile)) {
        unlink ($dir . $newFile);
        echo $file . "\n";
    }
}