$re = '/\/((?<prefix>[^\s\/]+)\/)*(?<fileName>.*)/';
$str = '1.(here file name should be data.csv)
/home/data/var/log/ data.csv
2.It doesn\'t have space after log
/home/data/var/log/data.csv
3.It has space with after log but file extension is different.(here file name is (data2015067987.dat)
/home/data/var/log/ data2015067987.dat
/home/data/var/log/ 201608587data.csv
4.(here file name is data data2 data3)
/home/data/var/log/ data data2 data3 ';
preg_match_all($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