Regular Expressions 101

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/
(\/[\D]{2}-((?!us).){2}\/)
/
gm
1st Capturing Group
(\/[\D]{2}-((?!us).){2}\/)
\/ matches the character / with index 4710 (2F16 or 578) literally (case sensitive)
Match a single character present in the list below
[\D]
{2} matches the previous token exactly 2 times
\D matches any character that's not a digit (equivalent to [^0-9])
- matches the character - with index 4510 (2D16 or 558) literally (case sensitive)
2nd Capturing Group
((?!us).){2}
{2} matches the previous token exactly 2 times
A repeated capturing group will only capture the last iteration. Put a capturing group around the repeated group to capture all iterations or use a non-capturing group instead if you're not interested in the data
Negative Lookahead
(?!us)
Assert that the Regex below does not match
us
matches the characters us literally (case sensitive)
. matches any character (except for line terminators)
\/ matches the character / with index 4710 (2F16 or 578) 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

Code Generator

Generated Code

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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