Regular Expressions 101

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/
\A(((?:[\w+\-].?)+)@([a-z\d\-]+(?:\.[a-z]+)*\.[a-z]+))\z
/
g
\A asserts position at start of the string
1st Capturing Group
(((?:[\w+\-].?)+)@([a-z\d\-]+(?:\.[a-z]+)*\.[a-z]+))
2nd Capturing Group
((?:[\w+\-].?)+)
Non-capturing group
(?:[\w+\-].?)+
+ matches the previous token between one 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 word character (equivalent to [a-zA-Z0-9_])
+ matches the character + with index 4310 (2B16 or 538) literally (case sensitive)
\- matches the character - with index 4510 (2D16 or 558) literally (case sensitive)
.
matches any character (except for line terminators)
? matches the previous token between zero and one times, as many times as possible, giving back as needed (greedy)
@ matches the character @ with index 6410 (4016 or 1008) literally (case sensitive)
3rd Capturing Group
([a-z\d\-]+(?:\.[a-z]+)*\.[a-z]+)
Match a single character present in the list below
[a-z\d\-]
+ matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
a-z matches a single character in the range between a (index 97) and z (index 122) (case sensitive)
\d matches a digit (equivalent to [0-9])
\- matches the character - with index 4510 (2D16 or 558) literally (case sensitive)
Non-capturing group
(?:\.[a-z]+)*
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
\. matches the character . with index 4610 (2E16 or 568) literally (case sensitive)
Match a single character present in the list below
[a-z]
+ matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
a-z matches a single character in the range between a (index 97) and z (index 122) (case sensitive)
\. matches the character . with index 4610 (2E16 or 568) literally (case sensitive)
Match a single character present in the list below
[a-z]
+ matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
a-z matches a single character in the range between a (index 97) and z (index 122) (case sensitive)
\z asserts position at the end of the string
Global pattern flags
g modifier: global. All matches (don't return after first match)
Your regular expression does not match the subject string.Try launching the debugger to find out why.

Regular Expression
No Match

/
/
g

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