Description:
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Since version 5.5.11 a substr_compare with a negative 3rd parameter (=offset, thus it should start counting from the end of the string) incorrectly reports equality.

See http://3v4l.org/8co5P

I believe the bug could have been introduced in this commit: https://github.com/datibbaw/php-src/commit/e292391b3899ed2d80a8f44dc94074d68328c6ea

What caught my eye is the introduced cast to an unsigned integer but I don't know if this really is the source of the bug.

Workaround: specify a length (absolute value of the negative offset)

Test script:
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var_dump(substr_compare("template", "_emplate", -8));
var_dump(substr_compare("template", "_emplate", -8, 8));

Expected result:
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int(21)
int(21)

Actual result:
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int(0)
int(21)