Your site has been running fine for three years. Nobody has logged into the hosting dashboard since the developer who built it moved on, and the annual invoice renews itself. On the last day of September, the platform underneath it changes a version number nobody at your association has ever looked at, and on the first of October some part of the site may simply stop working.
Pantheon is removing six versions of PHP on September 30, 2026. If your association or nonprofit site is hosted there and is still running one of them, the platform will not take your site offline. It will do something that is arguably harder to plan around: it will upgrade you automatically.
Where this comes from. The dates and behavior below are from Pantheon's own release notes and end-of-sale notices. This is a scheduled platform change that has been published since March, not a discovery or an incident.
What Is Actually Being Removed
Six versions come off the platform on September 30, 2026. Three of them reached end of sale on May 1, 2026, so this is the second step of a schedule already in motion rather than a surprise.
- PHP 5.6, 7.0 and 7.1 , long past their own end of life.
- PHP 7.2, 7.3 and 8.0. These reached end of sale on Pantheon on May 1, 2026.
PHP 7.4 is not on the list. That is worth stating plainly, because it is the version a lot of older association sites are actually sitting on, and a partial reading of the announcement could send someone into an unnecessary emergency upgrade.
The Part That Deserves Your Attention
Pantheon's documentation describes the behavior directly: sites still running a removed PHP version will be automatically upgraded to the oldest available PHP version at the time of removal, and if the site's software has not been updated for compatibility, this may result in broken functionality.
Read that as an uncontrolled upgrade rather than an outage. An outage is obvious and someone calls you. An automatic version jump is quieter and stranger. The homepage renders. The blog renders. Then a form stops submitting, or a payment callback throws a fatal error, or a plugin that has not been updated since 2021 takes the member portal down while everything else looks normal.
The failure mode is specific to the way association sites are built. The public pages are usually simple and will survive almost anything. The complicated parts, the AMS integration, the dues payment path, the event registration flow, the single sign-on handoff, are where old PHP assumptions live, and those are precisely the parts nobody clicks through on a normal day.
How to Find Out Where You Stand in Ten Minutes
None of this requires a developer, and none of it requires us. Four steps, all inside the Pantheon dashboard.
- Open the site's Settings, then PHP Version. It tells you what each environment is running. Check Dev, Test and Live separately. They can differ, and Live is the one that matters.
- Compare against the removal list. If you are on 7.4 or newer, you are outside this particular change and can stop here.
- If you are on a removed version, do not change it on Live first. Change it on Dev, click through the member-facing paths, and only then promote. An automatic upgrade on September 30 gives you no such control, which is the whole argument for moving first.
- Write down what broke, if anything. That list is your actual project scope, and it is usually much shorter than people fear, often a single abandoned plugin.
This Is Not the Only Date on Pantheon's Calendar
Two other platform changes land in the same window, and it is worth knowing about them now rather than in November.
- The filesystem migration. Pantheon is moving sites from Valhalla to a new filesystem backed by Cloud Storage FUSE. Migrations began on September 1, 2026 and run by tier: Basic on October 5, Performance on November 16, Elite on November 30. This is automatic and requires no action, but uploads and backups are what changed, so a media-heavy site is worth a smoke test afterwards.
- Solr. Solr support for WordPress and the Solr Power plugin reaches end of life on January 11, 2027, and Solr 3 is removed from the platform on February 9, 2027. If your site search runs on Solr, that is a Q1 project, not a Q4 one, but it is the kind of thing that is much cheaper to budget for in October than to discover in February.
Note the collision worth avoiding. Elite-tier sites migrate filesystems on November 30, which is the day before Giving Tuesday. If that is you, the sensible move is to finish any donation-page work well before that week and deploy nothing else while it happens.
If You Are Not on Pantheon
The specific dates above do not apply to you. The pattern does. Every managed host runs a version removal schedule, and most of them handle a stale site the same way, by moving it for you rather than leaving it on unsupported software indefinitely. WP Engine, Kinsta, Acquia and Platform.sh all publish their own timelines. The question to take to whoever holds your hosting account is simply which PHP version you are on and what happens when it is retired.
Who Can Stop Reading Here
If your site is on a maintenance retainer and somebody sends you a report you actually read, this is already handled. Confirm that PHP versions are inside that scope and go back to your week. Paying twice for the same coverage is not an improvement, and a competent partner will have moved you off PHP 8.0 months ago.
Equally, if your organization runs a brochure site with no forms, no logins and no payments, an automatic PHP upgrade will probably pass without incident. The risk here scales with how much your website actually does.
Why This Keeps Happening
The structural reason is not technical. A hosting account is usually opened by whoever built the site, billed to a card that renews quietly, and then never opened again. The platform sends its notices to the email address on that account, which may belong to a former staff member or a vendor you stopped working with. The notices are not ignored so much as undelivered.
That is the part worth fixing permanently, and it costs nothing. Find out who receives your hosting notifications, and make sure it is a person who still works at your organization.
What an Upgrade Usually Costs
The honest answer is that it is rarely the PHP upgrade itself. Changing the version is a dropdown. The work is whatever the version change exposes, and on an association site that tends to fall into three buckets.
- Nothing at all. The most common outcome for a site that has been kept reasonably current. You change the version on Dev, everything works, you promote it, and the whole exercise takes an afternoon.
- One abandoned plugin or module. The second most common. Something small, a slider, an old form handler, a social feed widget, that has not had a release in years and throws fatal errors on a newer PHP. Usually the fix is removal or replacement rather than repair.
- Custom integration code. The expensive case, and the one worth knowing about early. If somebody wrote bespoke code to connect your site to your AMS or your payment processor, and that person is no longer available, an automatic upgrade is a poor way to discover how it was written.
Find Out What You Are Running
Send us your hosting login or read us the PHP version off the dashboard, and we will tell you whether September 30 affects you, which of your plugins or modules are the ones that would actually break on an automatic upgrade, and what the compatibility work would take. You will get back a specific list with a recommendation next to every line, and a clear answer to the question the dashboard does not put in front of you: whether the first of October is a normal Thursday for your website or a bad one.