Description:
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substr_compare shouldn't output warning and return FALSE if the "length" parameter *equals* the length of main_str. It should do that only if length > strlen(main_str). 

Moreover an invalid error is returned: "The start position cannot exceed initial string length" even if specifying start position 0.

This error didn't exist in version 5.1.0.

Reproduce code:
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echo substr_compare("abcd","abcd",0,4);




Expected result:
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it should do the same as this (return 0):
echo substr_compare("abcd","abcd",0);


Actual result:
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Warning: substr_compare() [function.substr-compare]: The start position cannot exceed initial string length in ...