title: What is causing "Unable to allocate memory for pool" in PHP?
body: <p>I've occasionally run up against a server's memory allocation limit, particularly with a bloated application like Wordpress, but never encountered "Unable to allocate memory for pool" and having trouble tracking down any information.</p>
  
  <p>Does anyone know what this means?  I've tried increasing the <code>memory_limit</code> without success.  I also haven't made any significant changes to the application. One day there was no problem, the next day I hit this error.</p>