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Re: How i can get preg_match by url?

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Ben Bacarisse wrote:

> thaoluangiavang@gmail.com writes:
>> I want find all urls match with one url. i try code below:
>> <?php
>> $url_regex = '^http://toilatester.com/category/?xv=.*';
> 
> You need a delimiter round the pattern.

Not necessarily there, though.  The delimiter can also be with the function 
call in which $url_regex is used.  Also, with this line alone one cannot 
know if the final regular expression is constructed by concatenation, or 
used in different contexts, in a way that if the delimiter were inserted 
here already, it could break the code.  So one should be slow to make any 
changes in such a line.

> Most often that's / but in this case you'll end up having to quote all 
> those /s if you do that.

Note that preg_quote() is _not_ a general solution for this problem as it 
would quote all special characters that are part of the PCRE syntax, not 
only the specified delimiter.  If you only want to quote the delimiter 
automatically, you should use preg_replace() on the part of the expression 
between the delimiters (str_replace() may not suffice when the expression 
uses characters beyond the ISO-8859-1 range).

<http://php.net/preg_quote>

> You can use all sort of characters

The characters that can be used are limited:

$ php -r 'preg_match("fof", "foobar", $matches); print_r($matches);'
PHP Warning:  preg_match(): Delimiter must not be alphanumeric or backslash 
in Command line code on line 1
PHP Stack trace:
PHP   1. {main}() Command line code:0
PHP   2. preg_match('fof', 'foobar', NULL) Command line code:1

> but I like to use curly brackets.

Using “{” and “}” makes regular expressions harder to read in which 
repetition ranges (“a{1, 2}”) are used.

However, I was surprised that not only that a pair of “{” and “}” can be 
used in PHP (I had expected that to be Perl-specific), but that apparently 
they do not need to be escaped then:

$ php -r 'preg_match("{fo{2}}", "foobar", $matches); print_r($matches);'
Array
(
    [0] => foo
)

> Then you need to quote the special character ? so that it means a literal 
> ? and not, as yo currently have it, that the / is options.

Probably you mean _optional_.

> Also, you don't need .* at the end.

Depends.

> If the previous part matches it's going to match with .* also, and if the 
> previous part does *not* match it won't just because you got .* there:

However, if the expression before “.*” matches, then “.*” would match all 
characters until the end of the line (without PCRE_DOTALL) or the text (with 
PCRE_DOTALL).  Matching does not necessarily mean only testing.

  Text:   http://toilatester.com/category/?xv=foobarbaz
          ^-------------------------------------------^
  RE:    ^http://toilatester.com/category/?xv=.*
  Match:  http://toilatester.com/category/?xv=foobarbaz

vs.

  Text:   http://toilatester.com/category/?xv=foobarbaz
          ^----------------------------------^
  RE:    ^http://toilatester.com/category/?xv=
  Match:  http://toilatester.com/category/?xv=

$ php -r 'preg_match_all("`http://foo.example/.*`", 
"http://foo.example/bar\nx\nhttp://foo.example/baz", $matches); 
print_r($matches);'
Array
(
    [0] => Array
        (
            [0] => http://foo.example/bar
            [1] => http://foo.example/baz
        )

)

$ php -r 'preg_match_all("`http://foo.example/`", 
"http://foo.example/bar\nx\nhttp://foo.example/baz", $matches); 
print_r($matches);'
Array
(
    [0] => Array
        (
            [0] => http://foo.example/
            [1] => http://foo.example/
        )

)

-- 
PointedEars
Zend Certified PHP Engineer 
<http://www.zend.com/en/yellow-pages/ZEND024953> | Twitter: @PointedEars2
Please do not cc me. / Bitte keine Kopien per E-Mail.

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Thread

How i can get preg_match by url? thaoluangiavang@gmail.com - 2016-01-07 20:03 -0800
  Re: How i can get preg_match by url? "R.Wieser" <address@not.available> - 2016-01-08 10:15 +0100
  Re: How i can get preg_match by url? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-01-08 11:42 +0000
    Re: How i can get preg_match by url? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-01-09 10:55 +0100
      Re: How i can get preg_match by url? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-01-09 11:00 +0100
  Re: How i can get preg_match by url? SM Bestvideo <thaoluangiavang@gmail.com> - 2016-01-08 20:46 -0800
    Re: How i can get preg_match by url? Luuk <luuk@invalid.lan> - 2016-01-09 11:17 +0100

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