Description:
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The only way to set *no context* to fopen() is to not set the 4th parameter.

This should be changed to accept NULL as 4th parameter, leading to *no context*.

Why?

 1) consistency. At least three related functions accepts NULL

 2) enables to set the context dynamically, eg avoiding if ($context) fopen (.., $context) else fopen (..)

 3) not a BC break, unless you include previously broken code


Test script:
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file_put_contents ('/tmp/foo', 'bar', 0, NULL);

file_get_contents ('/tmp/foo', false, NULL);

file ('/tmp/foo', 0, NULL);

fopen ('/tmp/foo', 'r', false, NULL);

Expected result:
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No warning

Actual result:
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"PHP Warning:  fopen() expects parameter 4 to be resource, null given"