Regular Expressions 101

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  • Unit Tests (7)
/
^(?=.*?[A-Z])(?=(.*[a-z]){1,})(?=(.*[\d]){1,})(?=(.*[\W]){1,})(?!.*\s).{8,25}$
/
gm
^ asserts position at start of a line
Positive Lookahead
(?=.*?[A-Z])
Assert that the Regex below matches
.
matches any character (except for line terminators)
*? matches the previous token between zero and unlimited times, as few times as possible, expanding as needed (lazy)
Match a single character present in the list below
[A-Z]
A-Z matches a single character in the range between A (index 65) and Z (index 90) (case sensitive)
Positive Lookahead
(?=(.*[a-z]){1,})
Assert that the Regex below matches
1st Capturing Group
(.*[a-z]){1,}
{1,} matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
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
.
matches any character (except for line terminators)
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
Match a single character present in the list below
[a-z]
a-z matches a single character in the range between a (index 97) and z (index 122) (case sensitive)
Positive Lookahead
(?=(.*[\d]){1,})
Assert that the Regex below matches
2nd Capturing Group
(.*[\d]){1,}
{1,} matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
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
.
matches any character (except for line terminators)
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
Match a single character present in the list below
[\d]
\d matches a digit (equivalent to [0-9])
Positive Lookahead
(?=(.*[\W]){1,})
Assert that the Regex below matches
3rd Capturing Group
(.*[\W]){1,}
{1,} matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
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
.
matches any character (except for line terminators)
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
Match a single character present in the list below
[\W]
\W matches any non-word character (equivalent to [^a-zA-Z0-9_])
Negative Lookahead
(?!.*\s)
Assert that the Regex below does not match
.
matches any character (except for line terminators)
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
\s matches any whitespace character (equivalent to [\r\n\t\f\v ])
.
matches any character (except for line terminators)
{8,25} matches the previous token between 8 and 25 times, as many times as possible, giving back as needed (greedy)
$ asserts position at the end of a line
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