Regular Expressions 101

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An explanation of your regex will be automatically generated as you type.
Detailed match information will be displayed here automatically.
  • All Tokens
  • Common Tokens
  • General Tokens
  • Anchors
  • Meta Sequences
  • Quantifiers
  • Group Constructs
  • Character Classes
  • Flags/Modifiers
  • Substitution
  • A single character of: a, b or c
    [abc]
  • A character except: a, b or c
    [^abc]
  • A character in the range: a-z
    [a-z]
  • A character not in the range: a-z
    [^a-z]
  • A character in the range: a-z or A-Z
    [a-zA-Z]
  • Any single character
    .
  • Alternate - match either a or b
    a|b
  • Any whitespace character
    \s
  • Any non-whitespace character
    \S
  • Any digit
    \d
  • Any non-digit
    \D
  • Any word character
    \w
  • Any non-word character
    \W
  • Non-capturing group
    (?:...)
  • Capturing group
    (...)
  • Zero or one of a
    a?
  • Zero or more of a
    a*
  • One or more of a
    a+
  • Exactly 3 of a
    a{3}
  • 3 or more of a
    a{3,}
  • Between 3 and 6 of a
    a{3,6}
  • Start of string
    ^
  • End of string
    $
  • A word boundary
    \b
  • Non-word boundary
    \B

Regular Expression
No Match

/
/
gix

Test String

Substitution

Processing...

Code Generator

Language

Generated Code

$re = '/(?(DEFINE) (?<palindrome> # Recursive alternative first to match recursive palindromes. # Invert alternatives order to match nested palindromes individually # and (drastically) reduce backtracking. (?<l1>\p{L})\p{M}* [\s\p{P}]* (?&palindrome) [\s\p{P}]* \k<l1>\p{M}* | (?<l2>\p{L})\p{M}* [\s\p{P}]* \k<l2>\p{M}* | \p{L}\p{M}* ) ) (?<=[\s\p{P}]|^) (?&palindrome) (?(?=\s*\p{P}) (?:\s*\p{P})+ | (?=\s|$))/ix'; $str = '~ should not match jambon ~ Simple a bb cc ddd bob ara abbb a radar essayasse ~ Spaces, diacritics and punctuation Don\'t nod!Step on no pets. Ésope reste ici et se repose. Élu par cette crapule ! ? Tu l\'as trop écrasé, César, ce Port-Salut ! Zeus a été à Suez. ~ Recursive palindromes a a ! ah ha ! abba / ab b a ~ abba été àb ba ~ abba, ab b a, abbà été àb ba'; $subst = "[$0]"; $result = preg_replace($re, $subst, $str); echo "The result of the substitution is ".$result;

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