Given that they were using PHP [IIUC], not really.
PHP is pretty much actively hostile to software engineering with it's weak typing, implicit type conversions all over the place, and propensity for "what the hell, let it on through" attitude on errors. (Plus there no separation of interface and implementation, which could go a long way toward modularizing the program's subsystems.)
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THEY USED PHP????!??!??!??!??!??!
Unfixable. This thing may never work.
That said, FR runs on PHP, but it is the brainchild of one person (more manageable), much smaller scope (more manageable), and evolved over 12 years (more manageable) — and it still has some bugs.
I am a Web/Software Developer/ System Admin who works primarily in PHP (also JS, JQuery, Linux - LAMP stack for short). Some of the biggest web systems out there are PHP based. Facebook, Yahoo, Amazon just to name a few.
You can see a full list here. Also, many of the initial errors I saw were java errors (tomcat server stack errors). In short, PHP is not the problem here.
As a programmer with almost 14 years under my belt, let me also state that I've worked on some pretty busy web systems (including ones now that help deliver news and commentary to many of you every day), and none of them had 5 million lines of code. That sounds like either hype, some contractor trying to hike up their fees, or complete spaghetti code.
But let's look at the bigger technical web picture here...
From a webdev standpoint, The HealthCare.gov website's functions should be as follows:
Sorry folks, but all that is Web Development 101, and even other government websites that do the same thing seem to work without a problem. I estimate the HealthCare.gov site could have been written in no more than 5000-6000 lines of code using existing open-source frameworks (and that's being generous).
From the reports I have read and the errors reports many of my colleagues have passed around, no load testing, unit testing, and very little Q/A was done with the site itself. Large, corporate web sites were build better for a fraction of the costs, and no errors.
In fact, the entire roll out of HealthCare.gov has been flawed. Let me put this in non-geek terms so everyone can understand:
Say Black Friday is coming. Right now, the big-box corps (Sears, Wal-Mart, Target, etc) are working on their promotions - a full rollout to start promoting BEFORE Thanksgiving, right? We're talking TV, radio, print AND web - all to start in November. Did you see any of this with failed HealthCare.gov?
No, you only saw Oct 1 get here, and media people could not even complete a form. Again, the whole rollout was flawed from the beginning, and if the Tea-Party fight forced the White House to push the site out before it's time - which many of us suspect, then Ted Cruz et al did their job - perhaps without even knowing it. Someone high up HAD to have seen these errors, and said "Launch it anyway"
I could go on, but I need to run into yet another scrum meeting, with other web developers.