Regular Expressions 101

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  • PCRE2 (PHP >=7.3)
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/
^[+a-z0-9_.+-]\@(?:[+a-z0-9-]\.)+[{2,63}a-z0-9]$
/
i
^ asserts position at start of the string
Match a single character present in the list below
[a-z0-9_.+-]
+ 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 insensitive)
0-9 matches a single character in the range between 0 (index 48) and 9 (index 57) (case insensitive)
_.+ matches a single character in the list _.+ (case insensitive)
- matches the character - literally (case insensitive)
This hyphen is treated literally, which might be confusing for others. Consider escaping it or placing at the start or end of the class!
\@ matches the character @ literally (case insensitive)
Non-capturing group
(?:[+a-z0-9-]\.)+
+ 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
[a-z0-9-]
+ 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 insensitive)
0-9 matches a single character in the range between 0 (index 48) and 9 (index 57) (case insensitive)
- matches the character - literally (case insensitive)
This hyphen is treated literally, which might be confusing for others. Consider escaping it or placing at the start or end of the class!
\. matches the character . literally (case insensitive)
Match a single character present in the list below
[a-z0-9]
{2,63} matches the previous token between 2 and 63 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 insensitive)
0-9 matches a single character in the range between 0 (index 48) and 9 (index 57) (case insensitive)
$ asserts position at the end of the string
Global pattern flags
i modifier: insensitive. Case insensitive match (ignores case of [a-zA-Z])
Your regular expression does not match the subject string.

Regular Expression
No Match

/
/
i

Test String