Description:
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It would be really useful if the mkdir function with the $recursive parameter set to TRUE would behave the same way as mkdir -p command on linux.

The difference between the two is that mkdir -p does not report an error if the directory already exists while the php version does.

And triggering a WARNING seems a bit too much, why not trigger a NOTICE or nothing at all when the directory already exists?

If backwards compatibility is a concern then we can create a new function called "mkdirp($path, $perm)".

Test script:
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<?php

var_dump(mkdir('/tmp/a/b/c/d/', 0777, true));
var_dump(mkdir('/tmp/a/b/c/d/', 0777, true));

Expected result:
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bool(true)
bool(true)

Actual result:
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bool(true)
bool(false)