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

/
/
mg

Test String

Substitution

Processing...

Code Generator

Language

Generated Code

$re = '/^(((\r?\n|\s)*[A-Za-z0-9+\/]){4})*(((\r?\n|\s)*[A-Za-z0-9+\/]){2}(=(\r?\n|\s)*){2}|((\r?\n|\s)*[A-Za-z0-9+\/]){3}(=(\r?\n|\s)*))?$/m'; $str = ' This is a good test to check for base64 encoded strings because it forces the string to begin and end in its own line== Arriba Cachipurriana 00000000: 4e 18 ac 8a c6 a0 a2 87 6d 7a cb 6d a1 c8 5e 72 :N.......mz.m..^r 00000010: 47 e8 ad b6 ac 7b ae 1e 9d ca 1d 79 db 2d ae 29 :G....{.....y.-.) 00000020: e0 b1 b7 9c 6a eb 1e 8a d7 e8 ad c7 ac b6 17 ac :....j........... 00000030: b6 b8 a7 82 da 1b 7a 08 a7 6a 77 5e 9d d8 a7 8a :......z..jw^.... 00000040: db 28 c2 79 62 9d :.(.yb. 00000046. -- CglUaGlzIGlzIGEgZ29vZCB0ZXN0IAp0byBjaGVjayBmb3IgYmFzZTY0IGVuY29kZWQgCnN0cmlu Z3MgYmVjYXVzZSBpdCBmb3JjZXMgCnRoZSBzdHJpbmcgdG8gYmVnaW4gYW5kIGVuZCAKaW4gaXRz IG93biBsaW5lPT0KQXJyaWJhIENhY2hpcHVycmlhbmEKMDAwMDAwMDA6IDRlIDE4IGFjIDhhIGM2 IGEwIGEyIDg3IDZkIDdhIGNiIDZkIGExIGM4IDVlIDcyIDpOLi4uLi4uLm16Lm0uLl5yCjAwMDAw MDEwOiA0NyBlOCBhZCBiNiBhYyA3YiBhZSAxZSA5ZCBjYSAxZCA3OSBkYiAyZCBhZSAyOSA6Ry4u Li57Li4uLi55Li0uKQowMDAwMDAyMDogZTAgYjEgYjcgOWMgNmEgZWIgMWUgOGEgZDcgZTggYWQg YzcgYWMgYjYgMTcgYWMgOi4uLi5qLi4uLi4uLi4uLi4KMDAwMDAwMzA6IGI2IGI4IGE3IDgyIGRh IDFiIDdhIDA4IGE3IDZhIDc3IDVlIDlkIGQ4IGE3IDhhIDouLi4uLi56Li5qd14uLi4uCjAwMDAw MDQwOiBkYiAyOCBjMiA3OSA2MiA5ZCAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICA6Ligu eWIuCjAwMDAwMDQ2Cg== '; $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