202004-03.date-parsing-example.php

<?php

function parse($input) {
  $formats = array(
    '/^\d{1,2}\.\d{1,2}\.\d{4}$/' => 'd.m.Y',
    '/^\d{8}$/' => 'dmY'
  );

  foreach($formats as $pattern => $format) {
    if(preg_match($pattern, $input)) {
      return DateTime::createFromFormat($format, $input);
    }
  }

  return null;
}

$tests = array('1.2.2001', '26081989');

foreach($tests as $test) {
  $result = parse($test);

  $resultString = $result ? $result->format('Y-m-d') : 'null';
  echo "Parsing '$test' as '$resultString'.\n";
}