$re = '/(\d\d\d\d)-(\d\d)(-\d\d\D)?/';
$str = 'ABC 2012-10-01
DEF 2013-07-10
2018-01-21
ABG 2015-10-30A
EDF 2019-01-19B
ABC/DEF/GEH 2019-01-19A
';
$subst = "";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
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