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

/
/
g

Test String

Code Generator

Language

Generated Code

$re = '/\{(?:(?:\{(?:(?:\{(?:[^{}])*\})|(?:[^{}]))*\})|(?:[^{}]))*\}/'; $str = 'captures up to singly-nested blocks: p{1} = \\{(?:[^{}])*\\} int main() { return 0; } captures up to doubly-nested: p{2} = \\{(?:(?:p{1})|(?:[^{}]))*\\} ...or... p{2} = \\{(?:(?:\\{(?:[^{}])*\\})|(?:[^{}]))*\\} void more_complex_fxn(int z) { int x = z / 9; if (x > 3) { do_something; x += 5; } } Following the pattern set above... up to triply-nested: p{3} = \\{(?:(?:p{2})|(?:[^{}]))*\\} ...or... p{3} = \\{(?:(?:\\{(?:(?:\\{(?:[^{}])*\\})|(?:[^{}]))*\\})|(?:[^{}]))*\\} double so_many_blocks(double x) { double y = x; while(y > 4) { if (y < 6) { y -= 0.3; } else { y -= 0.5; } } return y; }'; preg_match_all($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