$re = '/^.*?_ExampleXML_(.*?)_[^_]+\.xml$/m';
$str = 'First_ExampleXML_Only_This_Should_Be_Name_20211234567.xml
Second_ExampleXML_OnlyThisShouldBeName_202156789.xml
Third_ExampleXML_Only_This_Should_Be_Name1_2021445678.xml
Fourth_ExampleXML_Only_This_Should_Be_Name2_20214567.xml';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php