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

r"
"
gmx

Test String

Code Generator

Language

Generated Code

$re = '/(?<!\d) (?: (?!0000)[0-9]{4} (?P<sep1>[-/.])? (?: (?:(?(sep1)0?|0)[1-9]|1[0-2]) (?P=sep1) (?:(?(sep1)0?|0)[1-9]|1[0-9]|2[0-8]) |(?:(?(sep1)0?|0)[13-9]|1[0-2]) (?P=sep1) (?:29|30) |(?:(?(sep1)0?|0)[13578]|1[02]) (?P=sep1) (?:31) ) | (?: [0-9]{2} (?: 0[48] |[2468][048] |[13579][26] ) |(?: 0[48] |[2468][048] |[13579][26] )00 ) (?P<sep2>[-/.]?) (?(sep2)0?|0)2 (?P=sep2) (?:29) ) (?!\d) /mx'; $str = 'aaa_20150229_bbb aaa_2012-02-29_bbb aaa_2000-02-29_bbb aaa_20000229_bbb 2004-2-29 1696-2-29 16960229 aaa_1904229_bbb aaa_18000229_bbb aaa_17000229_bbb aaa_16000229_bbb 2019-3-30 19960229 aaa_20150130_bbb aaa_20150131_bbb aaa_2015-04-30_bbb aaa_20150431_bbb 2019228 2019228 201911'; preg_match_all($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