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

/
/
xgJ

Test String

Code Generator

Language

Generated Code

$re = '/(?(DEFINE) (?<add> \s*\+\s* ) (?<eq> \s*=\s* ) (?<carry> (?(cl)(?(cr)|\d0)|(?(cr)\d0|(*F))) ) (?<b> (?&add) (?:\d*(?:0|1(?<r1>)))? (?(ro)|(?=(?<cr>1)?)) (?=\k<e> (?&eq) \d*(?(?=(?(l1)(?(r1)|(*F))|(?(r1)(*F))))(?(?=(?&carry))1|0)|(?(?=(?&carry))0|1))\k<f>\b) | (?=\d* (?&add) (?:\k<e>(?<ro>)|\d*(?<e>\d\k<e>)) (?&eq) \d*(?<f>\d\k<f>)\b) \d(?&b) ) (?<s> (?:0|1(?<l1>))(?=(?<cl>1)?\d*(?<e>) (?&add) \d* (?&eq) \d*(?<f>)\b)(?&b) ) ) \b(?=(?:(?=(?&s))\d)+)[01]+(?&add)[01]+(?&eq)[01]+\b/xJ'; $str = '1 + 1 = 1 0 + 1 = 1 01 + 10 = 11 010 + 010 = 100 101 + 10 = 111 101 + 10 = 101 11 + 101 = 1000 010 + 010 = 000 '; preg_match_all($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