How to Prevent Duplicate Customer Records When Converting Leads in PHP

A developer building a custom CRM in PHP and MySQL has shared a practical pattern for safely converting leads into customers without creating duplicate records. The core challenge is that clicking a 'Convert' button should not blindly insert a new customer row if that person already exists in the database. The approach prioritizes matching by email address first, then falls back to phone number, using PDO prepared statements for each lookup. If a match is found, the existing customer ID is reused; only when no match exists should a new customer record be inserted. The author notes that name-based matching is unreliable due to variations in spelling and formatting, making contact details stronger identifiers.