$re = '/\b(\w?)(\w?)(\w?)(\w?)(\w?)(\w)\S?\6\5\4\3\2\1\b/';
$str = 'tattarrattat –
aibohphobia – a joke word meaning "fear of palindromes", deliberately constructed so as to be one (various other words have been contrived along these lines, such as ailihphilia, a love of palindromes, elihphile, a lover of palindromes, etc.)
detartrated – past tense of “to detartrate”, a chemical term meaning to remove tartrates; alternatively an adjective indicating that tartrates have indeed been removed (this is the longest English palindrome in the Guinness Book of Records, though it is not listed in dictionaries; it is, however, encountered in some discussions of Concord grape juice [1])
kinnikinnik – variant (or common misspelling) of kinnikinnick, a Native American smoking mixture
Aoxomoxoa – A 1969 album by the Grateful Dead.
Malayalam – An Indian dialect (Mother tongue of Keralites).
deleveled – past tense and past participle of "delevel", to demote or be demoted to a lower level.
evitative – a grammatical case indicating fear or aversion.
redivider – someone or something that redivides (tied for longest "real" palindrome that is not a proper noun and that appears in English dictionaries).
releveler – (American spelling) someone or something that levels again (tied for longest "real" palindrome that is not a proper noun and that appears in English dictionaries).
Rotavator – a type of machine for breaking up soil (trademark)
Seven letters
Adinida – a suborder of planktonic organisms
deified – past tense of "to deify", meaning to consider as a god
hadedah – a type of S. African grey ibis
murdrum – in old English law, a secret killing
Nauruan – the language spoken in Nauru
peeweep – a type of bird, often understood to be a lapwing
racecar – a racing car
reifier – someone who reifies (considers an abstract concept to be real)
repaper – to cover again with paper
reviver – someone or something that revives or restores
rotator – a thing that rotates
seities – plural of seity, the essence of an individual
sememes – plural of sememe, the interpretation given to a morpheme (a language unit)
Senones – an ancient people who lived in part of what is now France
soosoos – plural of soosoo, a type of dolphin
degged - past tense of to deg, meaning to water a plant
denned – past tense of to den, meaning to live in a den
hallah – a variant of challah, a special Jewish braided bread eaten on Sabbath and Jewish holidays.
mallam – in West Africa, a learned man
marram – a type of grass
pip-pip – an old-fashioned British word for good-bye
pull-up or pullup – an exercise in which one pulls oneself up by the arms
redder – more red
renner – an archaic variant of runner
revver – someone or something that revs (an engine)
selles – plural of selle, an archaic word for a saddle
sesses – plural or third-person present tense of sess, an archaic word for tax (a variant of assess)
succus – any of various liquids excreted by animals or plants
terret – a metal ring on a harness, through which the reins pass
tirrit – according to Webster’s Dictionary (1913): "A word from the vocabulary of Mrs. Quickly, the hostess in Shakespeare’s Henry IV., probably meaning terror"
tut-tut – a disapproving sound; to make such a sound
solos – plural of solo
stats – contraction of statistics
stets – third-person present tense of "to stet", meaning to indicate that a passage of text should remain unchanged
stots – third-person present tense of "to stot", meaning to leap or bounce
sulus – plural of sulu, a type of sarong
Susus – plural of Susu, a member of a West African people
tenet – a belief or principle
torot – see [2], [3]
Wakaw - A town and a lake in Saskatchewan, Canada.
Xanax - Pfizer\'s trade name for alprazolam, a benzodiazepene used to treat panic disorder (severe anxiety and panic attacks).
Anna – a girl’s name
Beeb – an informal name for the BBC
boob – a blunder; a breast
deed – various common meanings
esse – existence or essence
goog – an egg (Australian slang)
immi – a Swiss unit of volume
keek – to peep
kook – a crazy person
ma\'am – a contraction of madam
otto – variant of attar, an essential oil
Otto - a proper name
peep – various common meanings
poop – a raised deck at the stern of a ship; various other meanings
sees – third-person present tense of ‘to see’
toot – the sound made by a\\
pip – a seed; also, to get the better of
pop – a cola; also, to burst
pup – the young of any of various mammals
sis – shortened form of "sister"
sos – plural of "so", the fifth tone of the diatonic scale in music
tat – tattoo
tet – the ninth letter of the Hebrew alphabet
tit – a small bird (British); a br\\
zzz – the sound of snoring
aa – lava having a rough surface (pron. a’a’)
ee – an extinct Hawaiian bird (pron. e’e’)
mm – used to express satisfaction';
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