500 The FastCGI process exited unexpectedly

Recently at work, I’ve came across the error “500 The FastCGI process exited unexpectedly” error code: 0xc0000005, trying to execute a PHP script on an IIS6 and IIS7 server. Knowing how annoying it was to resolve and how many people have the same problem, I thought I would answer your questions.

The problem is caused by excessively requiring more memory than is allocated to your script, which depending on the version of PHP you are running, defaults between 8 and 128 megabytes. To work out how much memory your script is actually using, you should log usage at all points in your script (especially in large loops), this can be done using the functions:

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