Filling placeholders in the IN clause

bettermysql-in-clause.php

<?php
  // Assuming that database connection is already open
  // Get username
  $userIDs = array(10, 38, 56, 93);
  
  // Method 1: array_fill() then implode()
  $placeholders = implode(',', array_fill(0, count($userIDs), '?'));
  
  // Method 2: str_repeat() then str_split() then implode()
  $placeholders = implode(',', str_split(str_repeat('?', count($userIDs))));
  
  // Method 3: str_repeat() then substr()
  $placeholders = substr(str_repeat('?,', count($userIDs)), 0, -1);
  
  // Method 4: str_repeat() then append last placeholder
  $placeholders = str_repeat('?,', count($userIDs)-1).'?';
  
  // Prepare and execute statement
  $stmt = $db->prepare("SELECT user, email, country FROM users WHERE id IN ($placeholders)");
  $stmt->execute($userIDs);
?>