$re = '/^\d.*?\b\d{5}$/ms';
$str = 'asf aSD ikugfr jddc ghddfj gjn dfxg
sdgal fghfh 16 rgjodrisgj frth fghsdf,
dfghdf dfhgdh gho h ghdof 67676
szdgfads
2 adf dojosd hsh fghs,
zfgdf dhgdzsfb dfgdz,
dzgdzfvg 47564
asdgasdg asdg
4334 ersga errr ertgerfd ertera erers qereadf erfesfdc wefadfe,
sfsdgfg-43647
2 adf dojosd hsh fghs,
zfgdf dhgdzsfb dfgdz,
dzgdzfvg and more than 5 digits here 11147564';
preg_match_all($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