trim_word_left.php

<?php
function trim_word_left($s, array $words) {
    foreach ($words as $word) {
        while (($p = mb_strpos($s, $word)) === 0) {
            $s = mb_substr($s, $p + mb_strlen($word));
            $s = trim($s);
        }
    }
    return $s;
}
$s = 'fo kerem';
var_dump(trim_word_left($s, ['fo']));