Regular Expressions 101

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  • PCRE2 (PHP >=7.3)
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/
(?<!\d\.)\b\d{9}\b(?!\.\d)
/
gm
Negative Lookbehind
(?<!\d\.)
Assert that the Regex below does not match
\d matches a digit (equal to [0-9])
\. matches the character . literally (case sensitive)
\b assert position at a word boundary: (^\\w|\\w$|\\W\\w|\\w\\W)
\d{9}
matches a digit (equal to [0-9])
{9} Quantifier — Matches exactly 9 times
\b assert position at a word boundary: (^\\w|\\w$|\\W\\w|\\w\\W)
Negative Lookahead
(?!\.\d)
Assert that the Regex below does not match
\. matches the character . literally (case sensitive)
\d matches a digit (equal to [0-9])
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