Regular Expressions 101

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  • PCRE2 (PHP >=7.3)
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  • ECMAScript (JavaScript)
  • Python 2.7
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/
\[(?![^\]\[{}]{(?# no {)(?![^\]\[{}]}(?#or a pair of {})))[^\]]\[
/
gm
\[ matches the character [ literally (case sensitive)
Negative Lookahead
(?![^\]\[{}]{(?# no {)(?![^\]\[{}]}(?#or a pair of {})))
Assert that the Regex below does not match
Match a single character not present in the list below
[^\]\[{}]
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
\] matches the character ] literally (case sensitive)
\[ matches the character [ literally (case sensitive)
{} matches a single character in the list {} (case sensitive)
{ matches the character { literally (case sensitive)
Comment: no {
Negative Lookahead
(?![^\]\[{}]}(?#or a pair of {}))
Assert that the Regex below does not match
Match a single character not present in the list below
[^\]\[{}]
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
\] matches the character ] literally (case sensitive)
\[ matches the character [ literally (case sensitive)
{} matches a single character in the list {} (case sensitive)
} matches the character } literally (case sensitive)
Comment: or a pair of {}
Match a single character not present in the list below
[^\]]
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
\] matches the character ] literally (case sensitive)
\[ matches the character [ literally (case sensitive)
Global pattern flags
g modifier: global. All matches (don't return after first match)
m modifier: multi line. Causes ^ and $ to match the begin/end of each line (not only begin/end of string)
Your regular expression does not match the subject string.Try launching the debugger to find out why.

Regular Expression
No Match

/
/
gm

Test String

Regular Expressions 101

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