PHP正则表达式匹配带有全部大写字母的行与偶尔的连字符

Question

I'm trying to to convert an existing PHP regular expression to apply to a slightly different style of document.

Here's the original style of the document:

**FOODS - TYPE A** 
___________________________________ 
**PRODUCT** 
1) Mi Pueblito Queso Fresco Authentic Mexican Style Fresh Cheese; 
2) La Fe String Cheese 
**CODE** 
Sell by date going back to February 1, 2009 

And the successfully-running PHP Regex match code that only returns "true" if the line is surrounded by asterisks, and stores each side of the "-" as $m[1] and $m[2], respectively.

 if ( preg_match('#^\*\*([^-]+)(?:-(.*))?\*\*$#', $line, $m) ) { 
    // only for **header - subheader** $m[2] is set. 
    if ( isset($m[2]) ) { 
      return array(TYPE_HEADER, array(trim($m[1]), trim($m[2]))); 
    } 
    else { 
      return array(TYPE_KEY, array($m[1])); 
    } 
  } 

So, for line 1: $m[1] = "FOODS" AND $m[2] = "TYPE A"; Line 2 would be skipped; Line 3: $m[1] = "PRODUCT", etc.

The question: How would I re-write the above regex match if the headers did not have the asterisks, but still was all-caps, and was at least 4 characters long? For example:

FOODS - TYPE A 
___________________________________ 
PRODUCT
1) Mi Pueblito Queso Fresco Authentic Mexican Style Fresh Cheese; 
2) La Fe String Cheese 
CODE
Sell by date going back to February 1, 2009 

Thank you.

Answer 1

Along the lines of (don't forget the "u" flag for Unicode regexes):

^(?:\*\*)?(?=[^*]{4,})(\p{Lu}+)(?:\s*-\s*(\p{Lu}+))?(?:\*\*)?\s*$

^               # start of line
(?:\*\*)?       # two stars, optional
(?=[^*]{4,})    # followed by at least 4 non-star characters
(\p{Lu}+)       # group 1, Unicode upper case letters
(?:             # start no capture group
  \s*-\s*       #   space*, dash, space*
  (\p{Lu}+)     #   group 2, Inicode upper case letters
)?              # end no capture group, make optional
(?:\*\*)?       # two stars, optional
\s*             # optional trailing spaces
$               # end of line

EDIT: Simplified, as per the comments:

^(?=[A-Z ]{4,})([A-Z ]+)(?:-([A-Z ]+))?\s*$

^               # start of line
(?=[A-Z -]{4,}) # followed by at least 4 upper case characters, spaces or dashes
([A-Z ]+)       # group 1, upper case letters or space
(?:             # start no capture group
  -             #   a dash
  ([A-Z ]+)     #   group 2, upper case letters or space
)?              # end no capture group, make optional
\s*             # optional trailing spaces
$               # end of line

Contents of groups 1 and 2 must be trimmed before use.