I don't know how to do this pattern!!!

[KT1990]

The role name occurs immediately after the first ‘ a ‘

E.g.
'An Astounding Reflection of a Lumberjack And a ...'

Output shold be

Lumberjack
Boy
...
...

[Markus]

Read up on regular expressions, please.

php > $string = 'An Astounding Reflection of a Lumberjack And a';
php > preg_match('#a (.*?) #', $string, $matches);
php > var_dump($matches);
array(2) {
  [0]=>
  string(13) "a Lumberjack "
  [1]=>
  string(10) "Lumberjack"
}

Mark.