# Regular expression, requires a negative 0-wide assertion

Source: Internet
Author: User
To find a regular expression, a negative 0-wide assertion is required
Content
`1234567890234123789`

I just want to match the content that is not inside, that needs to match to
`7890234123789`

The following is my own writing of the regular, but did not succeed, hope advice
`(?!)`

------to solve the idea----------------------
Did not solve your problem, but encountered a strange problem in the process of solving
```\$str = <<
<>1234567890234123789EOF;There is one in the Handbook (?! pattern) Negative pre-check should be the meaning of "negative 0 wide assertion"Preg_match_all ('/(<=) \d+ (?=<\/a>)/', \$STR, \$m);//[0] = 123456Preg_match_all ('/(?

) /', \$STR, \$t 1);/*With  or  adjacent numbers are not obtained to[0] = 2345[1] = 7890234[2] = 23[3] = 78Individual Test 123Also can only get to 23*/\$str _space = <<
<>7890234123EOF;Preg_match_all ('/(?

) /', \$str _space, \$t 2);/*And  a space on or adjacent to the  number.[0] = 123456[1] = 7890234[2] = 123[3] = 789*/echo "";Print_r (\$m);Print_r (\$t 1);Print_r (\$t 2);echo "";```

------to solve the idea----------------------
It's easy to match only to 123456.
Did you delete it and the rest is what you asked for?
`\$s =<<< TXT1234567890234123789TXT;\$p = ' #\d+[\r\n]+# ';Preg_match_all ("/[^\r\n]+/", Preg_replace (\$p, ", \$s), \$m);Print_r (\$m);`
`Array(    [0] = = Array        (            [0] = 7890234            [1] = 123            [2] = 789        ))`

It must be explained that the regular expression of PHP does not fully implement the full functionality of the modern regular expression, the implementation of the assertion is incomplete
If you want to learn about regular expressions, you should do so in C # and Java environments
If you are in need of practical use, then you should use your brains and work

Support for regular expressions is provided by the PCRE (Perl Compatible Regular expression) library, an open source software that is written by Philip Hazel and is copyrighted by the University of Cambridge. Can be obtained at the following address: Ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/.
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