Regular Expressions 101

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  • PCRE2 (PHP >=7.3)
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"
(?<=This is)(.*)(?=sentence)
"
s
Positive Lookbehind
(?<=This is)
Assert that the Regex below matches
This is matches the characters This is literally (case sensitive)
1st Capturing Group
(.*)
.
matches any character
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
Positive Lookahead
(?=sentence)
Assert that the Regex below matches
sentence matches the characters sentence literally (case sensitive)
Global pattern flags
s modifier: single line. Dot matches newline characters
Your regular expression does not match the subject string.

Regular Expression
No Match

r"
"
s

Test String