Regular Expressions 101

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/
^(?P<major>0|[1-9]\d*)\.(?P<minor>0|[1-9]\d*)\.(?P<patch>0|[1-9]\d*)(?:-(?P<prerelease>(?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*)(?:\.(?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*))*))?(?:\+(?P<buildmetadata>[0-9a-zA-Z-]+(?:\.[0-9a-zA-Z-]+)*))?$
/
gm
^ asserts position at start of a line
Named Capture Group major
(?P<major>0|[1-9]\d*)
1st Alternative
0
0 matches the character 0 literally (case sensitive)
2nd Alternative
[1-9]\d*
Match a single character present in the list below
[1-9]
1-9 a single character in the range between 1 (index 49) and 9 (index 57) (case sensitive)
\d*
matches a digit (equal to [0-9])
* Quantifier — Matches between zero and unlimited times, as many times as possible, giving back as needed (greedy)
\. matches the character . literally (case sensitive)
Named Capture Group minor
(?P<minor>0|[1-9]\d*)
1st Alternative
0
0 matches the character 0 literally (case sensitive)
2nd Alternative
[1-9]\d*
Match a single character present in the list below
[1-9]
1-9 a single character in the range between 1 (index 49) and 9 (index 57) (case sensitive)
\d*
matches a digit (equal to [0-9])
* Quantifier — Matches between zero and unlimited times, as many times as possible, giving back as needed (greedy)
\. matches the character . literally (case sensitive)
Named Capture Group patch
(?P<patch>0|[1-9]\d*)
1st Alternative
0
0 matches the character 0 literally (case sensitive)
2nd Alternative
[1-9]\d*
Match a single character present in the list below
[1-9]
1-9 a single character in the range between 1 (index 49) and 9 (index 57) (case sensitive)
\d*
matches a digit (equal to [0-9])
Non-capturing group
(?:-(?P<prerelease>(?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*)(?:\.(?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*))*))?
? Quantifier — Matches between zero and one times, as many times as possible, giving back as needed (greedy)
- matches the character - literally (case sensitive)
Named Capture Group prerelease
(?P<prerelease>(?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*)(?:\.(?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*))*)
Non-capturing group
(?:\+(?P<buildmetadata>[0-9a-zA-Z-]+(?:\.[0-9a-zA-Z-]+)*))?
? Quantifier — Matches between zero and one times, as many times as possible, giving back as needed (greedy)
\+ matches the character + literally (case sensitive)
Named Capture Group buildmetadata
(?P<buildmetadata>[0-9a-zA-Z-]+(?:\.[0-9a-zA-Z-]+)*)
$ 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

Loading code sample...
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