$re = '/(?x) # free-spacing mode
(?(DEFINE)
# Within this DEFINE block, we\'ll define many subroutines
# They build on each other like lego until we can define
# a "big number"
(?<one_to_9>
# The basic regex:
# one|two|three|four|five|six|seven|eight|nine
# We\'ll use an optimized version:
# Option 1: four|eight|(?:fiv|(?:ni|o)n)e|t(?:wo|hree)|
# s(?:ix|even)
# Option 2:
(?:f(?:ive|our)|s(?:even|ix)|t(?:hree|wo)|(?:ni|o)ne|eight)
) # end one_to_9 definition
(?<ten_to_19>
# The basic regex:
# ten|eleven|twelve|thirteen|fourteen|fifteen|sixteen|seventeen|
# eighteen|nineteen
# We\'ll use an optimized version:
# Option 1: twelve|(?:(?:elev|t)e|(?:fif|eigh|nine|(?:thi|fou)r|
# s(?:ix|even))tee)n
# Option 2:
(?:(?:(?:s(?:even|ix)|f(?:our|if)|nine)te|e(?:ighte|lev))en|
t(?:(?:hirte)?en|welve))
) # end ten_to_19 definition
(?<two_digit_prefix>
# The basic regex:
# twenty|thirty|forty|fifty|sixty|seventy|eighty|ninety
# We\'ll use an optimized version:
# Option 1: (?:fif|six|eigh|nine|(?:tw|sev)en|(?:thi|fo)r)ty
# Option 2:
(?:s(?:even|ix)|t(?:hir|wen)|f(?:if|or)|eigh|nine)ty
) # end two_digit_prefix definition
(?<one_to_99>
(?&two_digit_prefix)(?:[- ](?&one_to_9))?|(?&ten_to_19)|
(?&one_to_9)
) # end one_to_99 definition
(?<one_to_999>
(?&one_to_9)[ ]hundred(?:[ ](?:and[ ])?(?&one_to_99))?|
(?&one_to_99)
) # end one_to_999 definition
(?<one_to_999_999>
(?&one_to_999)[ ]thousand(?:[ ](?&one_to_999))?|
(?&one_to_999)
) # end one_to_999_999 definition
(?<one_to_999_999_999>
(?&one_to_999)[ ]million(?:[ ](?&one_to_999_999))?|
(?&one_to_999_999)
) # end one_to_999_999_999 definition
(?<one_to_999_999_999_999>
(?&one_to_999)[ ]billion(?:[ ](?&one_to_999_999_999))?|
(?&one_to_999_999_999)
) # end one_to_999_999_999_999 definition
(?<one_to_999_999_999_999_999>
(?&one_to_999)[ ]trillion(?:[ ](?&one_to_999_999_999_999))?|
(?&one_to_999_999_999_999)
) # end one_to_999_999_999_999_999 definition
# ==== MORE ====
(?<one_to_quadrillion>
(?&one_to_999)[ ]quadrillion(?:[ ](?&one_to_999_999_999_999_999))?|
(?&one_to_999_999_999_999_999)
) # end one_to_quadrillion definition
(?<one_to_quintillion>
(?&one_to_999)[ ]quintillion(?:[ ](?&one_to_quadrillion))?|
(?&one_to_quadrillion)
) # end one_to_quintillion definition
(?<one_to_sextillion>
(?&one_to_999)[ ]sextillion(?:[ ](?&one_to_quintillion))?|
(?&one_to_quintillion)
) # end one_to_sextillion definition
(?<one_to_septillion>
(?&one_to_999)[ ]septillion(?:[ ](?&one_to_sextillion))?|
(?&one_to_sextillion)
) # end one_to_septillion definition
(?<one_to_octillion>
(?&one_to_999)[ ]octillion(?:[ ](?&one_to_septillion))?|
(?&one_to_septillion)
) # end one_to_octillion definition
(?<one_to_nonillion>
(?&one_to_999)[ ]nonillion(?:[ ](?&one_to_octillion))?|
(?&one_to_octillion)
) # end one_to_nonillion definition
(?<one_to_decillion>
(?&one_to_999)[ ]decillion(?:[ ](?&one_to_nonillion))?|
(?&one_to_nonillion)
) # end one_to_decillion definition
(?<bignumber>
zero|(?&one_to_decillion)
) # end bignumber definition
(?<zero_to_9>
(?&one_to_9)|zero
) # end zero to 9 definition
# (?<decimals>
# point(?:[ ](?&zero_to_9))+
# ) # end decimals definition
) # End DEFINE
####### The Regex Matching Starts Here ########
\b(?:(?&ten_to_19)\s+hundred|(?&bignumber))\b
#\b(?:(?&ten_to_19)\s+hundred|(?&bignumber)(?:[ ](?&decimals))?)\b # No decimals for now
### Other examples of groups we could match ###
#(?&bignumber)
# (?&one_to_99)
# (?&one_to_999)
# (?&one_to_999_999)
# (?&one_to_999_999_999)
# (?&one_to_999_999_999_999)
# (?&one_to_999_999_999_999_999)/m';
$str = 'one
twelve
seventy two
three hundred
twelve hundred
twelve thousand three hundred four
six million
six million four hundred thousand five
one hundred twenty three billion four hundred fifty six million seven hundred eighty nine thousand twelve
four decillion';
preg_match_all($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