Description:
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When using the function DOMDocument::schemaValidate, the string x@ is matched by ".(\.{0,1}){0}@" but not by ".(\.?){0}@" (i.e., the only difference is {0,1} vs. ?).

Test script:
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Code:
    $xdoc = new DomDocument;
    $xdoc->loadXML( file_get_contents( 'xml.xml' ) );
    $xdoc->schemaValidate( 'schema.xsd' );

Schema, schema.xsd:
    <?xml version="1.0" encoding="utf-8"?>
    <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
        <xs:element name="a">
            <xs:simpleType>
                <xs:restriction base="xs:string">
                    <xs:pattern value=".(\.{0,1}){0}@"></xs:pattern>
                </xs:restriction>
            </xs:simpleType>
        </xs:element>
    </xs:schema>

xml.xml:
    <?xml version="1.0" encoding="utf-8" standalone="yes"?>
    <a>x@</a>

Expected result:
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Validation expected.

Actual result:
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Warning: DOMDocument::schemaValidate(): Element 'a': [facet 'pattern'] The value 'x@' is not accepted by the pattern '.(\.{0,1}){0}@'.