title: What's the rationale behind the claim "PHP doesn't scale up (well)"?
body: <p>I've recently picked up PHP and it seems rather neat language enabling very quick web application development (probably faster than my personal favorite - Java :)</p>
  
  <p>Now, I'm no PHP expert - neither with the language nor its internals/specifics. But quite a few of my peers have made the claim that <em>PHP applications don't scale up well</em> - a fact that I've not been able to figure out for myself and hence the question.</p>
  
  <p>I've just learnt the procedural flavor of PHP and my only guess of non-scalability is that of <em>scalability</em> of procedural vs. OO languages (C vs. C++/Java). I agree and and I can see how that would be a hurdle for extremely complex web applications. However, I'm aware of OO-ness coming to the PHP world and don't see that to be much of a hurdle (please correct me if my hypothesis is incorrect).</p>
  
  <p>Other than that I don't understand what scalability problems would arise for a web application with a large number of users (for the sake of discussion, let's assume a Restful design - no sessions - since I am aware of how that impedes scalability). I'm more interested in knowing 'objective' reasons for such a claim, if possible. Subjectivity is fine but I'm not here to start a debate as to PHP vs. everything else. I'm only interested in knowing what are the potential limitations of this language that I must keep in mind and should not bite me in the behind later if/when the web application were to have 1000's of users a day (or hour).</p>