<?php
$pdo->query("create table test (t text)");
$pdo->query("insert into test (t) values ('222_222'),('2226_4444'),('2229_5556'),('22_33')");
$stmt = $pdo->query("select * from test where t like '222_%'");
echo json_encode($stmt->fetchAll(PDO::FETCH_COLUMN)),"\n";
$stmt = $pdo->query("select * from test where t like '222\_%'");
echo json_encode($stmt->fetchAll(PDO::FETCH_COLUMN)),"\n";