The verdict in three sentences
A PHP 5 app still in production is a time bomb: no more security patches, hosts dropping support, developers impossible to find. In 2026, modernizing it costs 25,000 to 80,000 EUR depending on code volume, with an unavoidable upfront audit of 2,500 to 6,000 EUR. The real hidden cost is an incident on an unpatched legacy system that can freeze your operations for days.
Upgrade, partial rebuild or full rewrite: three paths
Not every PHP 5 codebase deserves a full rewrite. The audit sorts your code into three scenarios, from cheapest to heaviest.
| Scenario | What we do | 2026 budget | Timeline |
|---|---|---|---|
| PHP 8 upgrade | Language + dependency update, same features | 25,000 - 40,000 EUR | 3 - 4 months |
| Partial rebuild | New foundation, reuse stable business logic | 40,000 - 60,000 EUR | 4 - 6 months |
| Full rewrite | New architecture, new stack | 60,000 - 80,000 EUR | 5 - 7 months |
The PHP 8 upgrade is enough when the code is structured and the need hasn't changed. As soon as the architecture holds the business back, a partial rebuild offers the best value-to-risk ratio.
Data migration, regression testing and maintenance: the forgotten items
Migrating the code isn't enough. Data migration and regression tests guarantee nothing breaks, and post-migration maintenance secures the first months.
| Line item | Detail | 2026 order of magnitude |
|---|---|---|
| Upfront audit | Code map, debt, security | 2,500 - 6,000 EUR |
| Data migration | Cleanup, mapping, transfer | 3,000 - 15,000 EUR |
| Regression testing | Automated test suites | 4,000 - 10,000 EUR |
| User training | Sessions + support | 1,500 - 4,000 EUR |
| Post-migration maintenance | 15% of build/year | 4,000 - 12,000 EUR/year |
| Cost of a legacy incident | 1-3 days downtime | 5,000 - 30,000 EUR |
Maintenance at 15% of build cost is the best insurance: it absorbs fixes in the first three months, when residual bugs surface.
Mini case study
Nadia, who runs a property management firm in Toronto, operates a PHP 5 mandate-tracking app, unpatched for four years. A 4,000 EUR audit finds the business logic sound, the architecture obsolete. She picks a partial rebuild at 48,000 EUR over 5 months, plus 8,000 EUR of data migration and 6,000 EUR of testing. A security incident last year cost her two days of downtime, roughly 12,000 EUR. Now secured and under maintenance at 7,200 EUR/year, she eliminates that recurring risk.
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FAQ
Why not just stay on PHP 5?
PHP 5 has had no security patches since late 2018; hosts are phasing it out. Every extra month raises the risk of an unpatched incident, measurable in days of downtime.
Is a PHP 8 upgrade always safer than a rewrite?
Safer and cheaper (25,000-40,000 EUR) when the code is clean. On an untested spaghetti base, an upgrade can cost as much as a rebuild: the audit decides.
How long does the migration take?
From 3 months for an upgrade to 7 months for a full rewrite. Code volume and existing documentation quality can double that timeline.
Will my data be preserved?
Yes, through a dedicated migration (3,000-15,000 EUR) with mapping and verification datasets. We migrate to a test environment before any production cutover.
Should I plan for maintenance after migration?
Yes: 15% of build cost per year. It covers first-month fixes and enhancements, and stops the app from becoming legacy again within three years.
Let's scope your project. Send us the PHP version, code volume and your uptime constraints, and we'll frame an upgrade, rebuild or rewrite with budget and schedule. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.
Mohamed Bah
Fondateur, Kolonell
Passionate about digital and entrepreneurship in Africa, Mohamed has been helping Sénégalese businesses with their digital transformation since 2020. Founder of Kolonell, he believes every SME deserves a professional and accessible online présence.
