I try to match this expression :
* ^X-Spam-Flag: YES
I use this code :
if(preg_match('\'* ^X-Spam-Flag: YES\'', $value))
But i have this error :
PHP Warning: preg_match(): Compilation failed: nothing to repeat at
offset 0
Problem with regex and * and ^ but can i correct that ?
You are missing your delimiters.
Change to:
preg_match('#\'* ^X-Spam-Flag: YES\'#', $value)
Or maybe you need:
preg_match('#\* \^X-Spam-Flag: YES#', $value)
You was near the solution, you have to escape ^ and * since these have a special meaning in a regex pattern:
if(preg_match('\'\* \^X-Spam-Flag: YES\'', $value))
If your escaped single quotes look strange and may be better replaced by / or ~ ... however these can be used as delimiters.
More informations about delimiters here: http://www.php.net/manual/en/regexp.reference.delimiters.php
To safely escape Regex special characters, you can simply use "preg_quote()", which adds backslashes in front of these characters.
if(preg_match('\'* ^X-Spam-Flag: YES\'', preg_quote($value)))
Related
I have a php code that needs to be matched for any of the following string using preg_match using this code
if(preg_match('/(image/gif)|(image/jpg)|(image/jpeg)/',$between))
{
echo "Match Found";
}
else
echo "Match Not Found";
but i get this error
Warning: preg_match() [function.preg-match]: Unknown modifier 'g' in C:\xampp\htdocs\project\extension.php on line 38
Any help will be appreciated....I googled alot but couldn't find solution...
You are using / as the delimiter character, so when it appears inside your regex you must escape it:
if(preg_match('/(image\/gif)|(image\/jpg)|(image\/jpeg)/',$between))
Alternatively, you can choose another delimiter:
if(preg_match('~(image/gif)|(image/jpg)|(image/jpeg)~',$between))
Replace your preg_match pattern with this:
'/(image\/gif)|(image\/jpg)|(image\/jpeg)/'
You should always escape characters like /
As long as you want / to be used inside regular expression - use ~ as a regex delimiter instead:
if(preg_match('~(image/gif)|(image/jpg)|(image/jpeg)~',$between))
^----------- ^--------
or even better:
if(preg_match('~image/(gif|jpe?g)~',$between))
I am trying to match a Youtube URL with regex to see if it is valid. This is my code:
if(preg_match('\bhttp://youtube.com/watch\?v=.*\b', $link))
{
echo "matched youtube";
}
But I'm getting an error:
Warning: preg_match() [function.preg-match]: Delimiter must not be alphanumeric or backslash in C:\xampp\htdocs\ajax\youtube.php on line 22
I'll admit I am a complete novice to regular expressions and I don't understand them much but I am trying to learn as I do this. I made the above regex using this online regex tool:
http://gskinner.com/RegExr/
and it works there. So what am I doing wrong and is there a better way to validate a youtube URL?
Thanks. :)
There's really no need for preg_match here:
$url = "http://youtube.com/watch?v=abc";
if(strpos($url, "http://youtube.com/watch?v=") === 0) {
echo "Valid";
}
PCRE require delimiters that separate the regular expressions and optional modifiers.
In this case the \ is assumed but \ is not a valid delimiter (see error message). Use a different character like ~:
preg_match('~\bhttp://youtube\.com/watch\?v=.*\b~', $link)
You should add addition delimeters to your regexp. This is used to supply optional parameters:
preg_match('"\bhttp://youtube.com/watch\?v=.*\b"', $link)
Symbol / is usually used as regexp delimeter, but in your case it'll force inner / to be escaped. So for more clear view I suggest to use ".
When using preg_match, then the regexp needs to be enclosed with proper delimiters.
For example:
preg_match('/\bhttp://youtube.com/watch\?v=.*\b/', $link)
In your example \b stands for word boundary, this is not a valid alphanumeric delimiter, hence the error message
i used bellow code to search and find if http is includes in $url address user enters
if (!preg_match("/http:///", $user_website)
but i got this error
Warning: preg_match() [function.preg-match]: Unknown modifier '/' in
i know its becuase of // of http but how work arround this !?
Instead of having to escape every / in URL regexes it's often useful to use preg_* alternative characters to mark the start/end of the pattern.
if (!preg_match("#http://#", $user_website)
The delimiter you are using / is found in the pattern as well. In such cases you can either escape the delimiter in the pattern:
if (!preg_match("/http:\/\//", $user_website)
or you can choose a different delimiter. This will keep the pattern clean and short:
if (!preg_match("#http://#", $user_website)
You can escape the slashes like the other answers mention, or alternatively you can use different delimiters, preferably characters you won't use in your regex:
preg_match('~http://~', ...)
preg_match('!http://!', ...)
And you don't really need regex for this. String matching should be enough:
if (strpos($user_website, 'http://') !== false) {
// do something
}
See: strpos()
Surely you must do
$parts = parse_url($my_url);
$parts['scheme'] will then contain the url scheme (might be 'http').
Escape / characters with \ characters.
You need to escape literal characters. Place a back-slash before your forward slashes.
http:// becomes http:\/\/
if (!preg_match("/http:\/\//", $user_website)
I am using a lib which uses
eregi($match="^http/[0-9]+\\.[0-9]+[ \t]+([0-9]+)[ \t]*(.*)\$",$line,$matches)
but as eregi is deprecated now, i want to convert above to preg_match. I tried it as below
preg_match($match="/^http/[0-9]+\\.[0-9]+[ \t]+([0-9]+)[ \t]*(.*)\$/i",$line,$matches)
but it throws an error saying Unknown modifier '[' in filename.php
any ideas how to resolve this issue?
Thanks
If you use / as the regex delimiter (ie. preg_match('/.../i', ...)), you need to escape any instances of / in your pattern or php will think it's referring to the end of the pattern.
You can also use a different character such as % as your delimiter:
preg_match('%^http/[0-9]+\.[0-9]+[ \t]+([0-9]+)[ \t]*(.*)$%i',$line,$matches)
You need to escape the delimiters inside the regular expression (in this case the /):
"/^http\\/[0-9]+\\.[0-9]+[ \t]+([0-9]+)[ \t]*(.*)\$/i"
But you could also chose a different delimiter like ~:
"~^http/[0-9]+\\.[0-9]+[ \t]+([0-9]+)[ \t]*(.*)\$~i"
You can try:
preg_match("#^http/[0-9]+\\.[0-9]+[ \t]+([0-9]+)[ \t]*(.*)\$#i",$line,$matches)
You can drop the the $match=
You are using / as the delimiter
and there is another / present in the
regex after http, which effectively
marks the end of your regex. When PHP
sees the [ after this it complains.
You can use a different set of
delimiters as # or escape the / after http
if (preg_match('(\p{Nd}{4}/\p{Nd}{2}/\p{Nd}{2}/\p{L}+)', '2010/02/14/this-is-something'))
{
// do stuff
}
The above code works. However this one doesn't.
if (preg_match('/\p{Nd}{4}/\p{Nd}{2}/\p{Nd}{2}/\p{L}+/u', '2010/02/14/this-is-something'))
{
// do stuff
}
Maybe someone could shed some light as to why the one below doesn't work. This is the error that is being produced:
A PHP Error was encountered
Severity: Warning
Message: preg_match()
[function.preg-match]: Unknown
modifier '\'
Try this: (delimit the regex with ())
if (preg_match('#\p{Nd}{4}/\p{Nd}{2}/\p{Nd}{2}/\p{L}+#', '2010/02/14/this-is-something'))
{
// do stuff
}
Edited
The modifier u is available from PHP 4.1.0 or greater on Unix and from PHP 4.2.3 on win32.
Also as nvl observed, you are using / as the delimiter and you are not escaping the / present in the regex. So you'lll have to use:
/\p{Nd}{4}\/\p{Nd}{2}\/\p{Nd}{2}\/\p{L}+/u
To avoid this escaping you can use a different set of delimiters like:
#\p{Nd}{4}/\p{Nd}{2}/\p{Nd}{2}/\p{L}+#
or
#\p{Nd}{4}/\p{Nd}{2}/\p{Nd}{2}/\p{L}+#
As a tip, if your delimiter is present in your regex, its better to choose a different delimiter not found in the regex. This keeps the regex clean and short.
In the second regex you're using / as the regex delimiter, but you're also using it in the regex. The compiler is trying to interpret this part as a complete regex:
/\p{Nd}{4}/
It thinks the next character after the second / should be a modifier like 'u' or 'm', but it sees a backslash instead, so it throws that cryptic exception.
In the first regex you're using parentheses as regex delimiters; if you wanted to add the u modifier, you would put it after the closing paren:
'(\p{Nd}{4}/\p{Nd}{2}/\p{Nd}{2}/\p{L}+)u'
Although it's legal to use parentheses or other bracketing characters ({}, [], <>) as regex delimiters, it's not a good idea IMO. Most people prefer to use one of the less common punctuation characters. For example:
'~\p{Nd}{4}/\p{Nd}{2}/\p{Nd}{2}/\p{L}+~u'
'%\p{Nd}{4}/\p{Nd}{2}/\p{Nd}{2}/\p{L}+%u'
Of course, you could also escape the slashes in the regex with backslashes, but why bother?