I am using php version 7.0.14. In spite of several good examples on stackoverflow, I cannot get my php regex to work. I've been trying for hours every conceivable combination. The problem comes in trying to allow periods and slashes, which must be escaped. I have tried enclosing the regex in double and single quotes. I have tried escaping with one backslash, two, three, four. It either errors out, lets everything through (like $) or does not allow periods and slashes.
$strStreet = "123 1/2 S. Main St. Apt. 1";
#$strRegEx = "/^[a-z0-9 ,#-'\/]{3,50}$/i";
$strRegEx = '/^[a-z0-9 ,#-\'\/]{3,50}$/i';
if (preg_match($strRegEx, $strStreet) === 0 ) {
print "bad address";
}
Thanks in advance for any help.
You have two issues here:
there is no . in your character class (in a character class the . doesn't need to be escaped)
the - in a character class needs to be escaped, or moved to the front or end (in other regex engines the escaping isn't available). On its own it creates a range of the characters on each side of it.
so:
^[-a-z0-9 ,#'\/.]{3,50}$
should work for you. (also if you use a different delimiter the forward slash won't need to be escaped)
Demo: https://regex101.com/r/PfZAlO/1/
Related
So I'm trying to check for match and if match, extract a variable name out of a string. The variable name should be preceded by "$" and cannot be escaped with "\", so for example "$name" should extract "name" and "\$name" or "name" shouldn't match. Heres the command:
$match = preg_match("/^(?<!\\)(\$.*)$/", $potential, $name);
I constructed and tested it using regex101.com and it works there, however, I'm getting an error from PHP saying
"preg_match(): Compilation failed: missing ) at offset 13 in ..."
and I have no clue what its referring to.
My thought is that you will need to escape certain characters to consume the regular expression in PHP
$match = preg_match('/^(?<!\\\\)(\$.*)$/', $potential, $name);
Edit: the backslash is the escape character in both Regex and PHP, you will need to doubly escape the slashes.
You've escaped a bracket:
preg_match('/^(?<!\\) <----HERE
FYI you can use several other delimiters to make your regex's more readable. Because so often we have slashes and escaped chars, then using '/' makes it hard to read. Consider using '#' or '~' or even '#' to increase readability.
Also reL your online regex tool of choice, it depends on which regular expression implementation (and version) the service uses, as to how accurate your results. I always use rubular.com (Uses PCRE) but for PHP you can use phpliveregex.com
Related question: How can I use regex to match a character (') when not following a specific character (?)?
I'm parsing a log using regex (PHP PCRE library), and trying to extract a URL from it. The URL is encapsulated in double quotes ", but some of the requests also include a double quote ". For example:
"https://www.amh.net.au/online/dbSearch.php?t=all&q=\"Rosuvastatin\""
My first pattern was basically:
#\"([^\"]*)\"#
This worked well, until I reached one of the entries as above, and it truncated the match so all I got was:
https://www.amh.net.au/online/dbSearch.php?t=all&q=\
After digging around, and rediscovering the cheatsheets for regex at http://addedbytes.com and also some more useful information at http://www.regular-expressions.info/lookaround.html I have now tried the following look-behind:
#"([(?<!\\)"]*)"#
But, now all I get is "" and then an empty string
You placed your lookbehind INSIDE your group ([]), so it's not interpreted as such, but rather just you say you only want those individual characters.
Basically, I think you'd like something like this:
#"(?:[^"]|(?<=\\)")"#
Though you should be aware that you'd be trolled by \\" for example.
The URLs in the logs would be URL-encoded. As such, the following pattern should work:
#\"([^ ]*)\"#
I am stuck trying to create a regex that will allow for letters, numbers, and the following chars: _ - ! ? . ,
Here is what I have so far:
/^[-\'a-zA-Z0-9_!\?,.\s]+$/ //not escaping the ?
and this version too:
/^[-\'a-zA-Z0-9_!\?,.\s]+$/ //attempting to escape the ?
Neither of these seem to be able to match the following:
"Oh why, oh why is this regex not working! It's getting pretty frustrating? Frustrating - that is to say the least. Hey look, an underscore_ I wonder if it will match this time around?"
Can somebody point out what I am doing wrong? I must point out that my script takes the user input (the paragraph in quotes in this case) and strips all white space so actual input has no white space.
Thanks!
UPDATE:
Thanks to Lix's advice, this is what I have so far:
/^[-\'a-zA-Z0-9_!\?,\.\s]+$/
However, it's still not working??
UPDATE2
Ok, based on input this is what's happening.
User inputs string, then I run the string through following functions:
$comment = preg_replace('/\s+/', '',
htmlspecialchars(strip_tags(trim($user_comment_orig))));
So in the end, user input is just a long string of chars without any spaces. Then that string of chars is run using:
preg_match("#^[-_!?.,a-zA-Z0-9]+$#",$comment)
What could possibly be causing trouble here?
FINAL UPDATE:
Ended up using this regex:
"#[-'A-Z0-9_?!,.]+#i"
Thanks all! lol, ya'll are going to kill me once you find out where my mistake was!
Ok, so I had this piece of code:
if(!preg_match($pattern,$comment) || strlen($comment) < 2 || strlen($comment) > 60){
GEEZ!!! I never bothered to look at the strlen part of the code. Of course it was going to fail every time...I only allowed 60 chars!!!!
When in doubt, it's always safe to escape non alphanumeric characters in a class for matching, so the following is fine:
/^[\-\'a-zA-Z0-9\_\!\?\,\.\s]+$/
When run through a regular expression tester, this finds a match with your target just fine, so I would suggest you may have a problem elsewhere if that doesn't take care of everything.
I assume you're not including the quotes you used around the target when actually trying for a match? Since you didn't build double quote matching in...
Can somebody point out what I am doing wrong? I must point out that my script takes the user input (the paragraph in quotes in this case) and strips all white space so actual input has no white space.
in which case you don't need the \s if it's working correctly.
I got the following code to work as expected to (running php5):
<?php
$pattern = "#[-'A-Z0-9_?!,.\s]+#i";
$string = "Oh why, oh why is this regex not working! It's getting pretty frustrating? Frustrating - that is to say the least. Hey look, an underscore_ I wonder if it will match this time around?";
$results = array();
preg_match($pattern, $string, $results);
echo '<pre>';
print_r($results);
echo '</pre>';
?>
The output from print_r($results) was as following:
Array
(
[0] => Oh why, oh why is this regex not working! It's getting pretty frustrating? Frustrating - that is to say the least. Hey look, an underscore_ I wonder if it will match this time around?
)
Tested on http://writecodeonline.com/php/.
It's not necessary to escape most characters inside []. However, \s will not do what you want inside the expression. You have two options: either manually expand (/^[-\'a-zA-Z0-9_!?,. \t\n\r]+$/) or use alternation (/^(?:[-\'a-zA-Z0-9_!?,.]|\s)+$/).
Note that I left the \ before the ' because I'm assuming you're putting this in a PHP string and I wouldn't want to suggest a syntax error.
The only characters with a special meaning within a character class are:
the dash (since it can be used as a delimiter for ranges), except if it is used at the beginning (since in this case it is no part of any range),
the closing bracket,
the backslash.
In "pure regex parlance", your character class can be written as:
[-_!?.,a-zA-Z0-9\s]
Now, you need to escape whatever needs to be escaped according to your language and how strings are written. Given that this is PHP, you can take the above sample as is. Note that \s is interpreted in character classes as well, so this will match anything which is matched by \s outside of a character class.
While some manuals recommend using escapes for safety, knowing the general regex rules for character classes and applying them leads to shorter and easier to read results ;)
i am looking for a regex that can contain special chracters like / \ . ' "
in short i would like a regex that can match the following:
may contain lowercase
may contain uppercase
may contain a number
may contain space
may contain / \ . ' "
i am making a php script to check if a certain string have the above or not, like a validation check.
The regular expression you are looking for is
^[a-z A-Z0-9\/\\.'"]+$
Remember if you are using PHP you need to use \ to escape the backslashes and the quotation mark you use to encapsulate the string.
In PHP using preg_match it should look like this:
preg_match("/^[a-z A-Z0-9\\/\\\\.'\"]+$/",$value);
This is a good place to find the regular expressions you might want to use.
http://regexpal.com/
You can always escape them by appending a \ in front of the special characters.
try this:
preg_match("/[A-Za-z0-9\/\\.'\"]/", ...)
NikoRoberts is 100% correct.
I would only add the following suggestion: When creating a PHP regex pattern string, always use: single-quotes. There are far fewer chars which need to be escaped (i.e. only the single quote and the backslash itself needs to be escaped (and the backslash only needs to be escaped if it appears at the end of the string)).
When dealing with backslash soup, it helps to print out the (interpreted) regex string. This shows you exactly what is being presented to the regex engine.
Also, a "number" might have an optional sign? Yes? Here is my solution (in the form of a tested script):
<?php // test.php 20110311_1400
$data_good = 'abcdefghijklmnopqrstuvwxyzABCDE'.
'FGHIJKLMNOPQRSTUVWXYZ0123456789+- /\\.\'"';
$data_bad = 'abcABC012~!###$%^&*()';
$re = '%^[a-zA-Z0-9+\- /\\\\.\'"]*$%';
echo($re ."\n");
if (preg_match($re, $data_good)) {
echo("CORRECT: Good data matches.\n");
} else {
echo("ERROR! Good data does NOT match.\n");
}
if (preg_match($re, $data_bad)) {
echo("ERROR! Bad data matches.\n");
} else {
echo("CORRECT: Bad data does NOT match.\n");
}
?>
The following regex will match a single character that fits the description you gave:
[a-zA-Z0-9\ \\\/\.\'\"]
If your point is to insure that ONLY characters in this range of characters are used in your string, then you can use the negation of this which would be:
[^a-zA-Z0-9\ \\\/\.\'\"]
In the second case, you could use your regex to find the bad stuff (that you don't want to be included), and if it didn't find anything then your string pattern must be kosher, because I'm assuming that if you find one character that is not in the proper range, then your string is not valid.
so to put it in PHP syntax:
$regex = "[^a-zA-Z0-9\ \\\/\.\'\"]"
if preg_match( $regex, ... ) {
// handle the bad stuff
}
Edit 1:
I've completely ignored the fact that backslashes are special in php double-quoted strings, so here is a correcting to the above code:
$regex = "[^a-zA-Z0-9\\ \\\\\\/\\.\\'\\\"]"
If that doesn't work it shouldn't take too much for someone to debug how many of the backslashes need to be escaped with a backslash, and what other characters need also to be escaped....
I'm looking for a simple replacement of [[wiki:Title]] into Title.
So far, I have:
$text = preg_replace("/\[\[wiki:(\w+)\]\]/","\\1", $text);
The above works for single words, but I'm trying to include spaces and on occasion special characters.
I get the \w+, but \w\s+ and/or \.+ aren't doing anything.
Could someone improve my understanding of basic regex? And I don't mean for anyone to simply point me to a webpage.
\w\s+ means "a word-character, followed by 1 or more spaces". You probably meant (\w|\s)+ ("1 or more of a word character or a space character").
\.+ means "one or more dots". You probably meant .+ (1 or more of any character - except newlines, unless in single-line mode).
The more robust way is to use
\[wiki:(.+?)\]
This means "1 or more of any character, but stop at first position where the rest matches", i.e. stop at first right bracket in this case. Without ? it would look for the longest available match - i.e. past the first bracket.
You need to use \[\[wiki:([\w\s]+)\]\]. Notice square brackets around \w\s.
If you are learning regular expressions, you will find this site useful for testing: http://rexv.org/
You're definitely getting there, but you've got a couple syntax errors.
When you're using multiple character classes like \w and \s, in order to match within that group, you have to put them in [square brackets] like so... ([\w\s]+) this basically means one or more of words or white space.
Putting a backslash in front of the period escapes it, meaning the regex is searching for a period.
As for matching special characters, that's more of a pain. I tried to come up with something quickly, but hopefully someone else can help you with that.
(Great cheat sheet here, I keep a copy on my desk at all times: http://www.addedbytes.com/cheat-sheets/regular-expressions-cheat-sheet/ )