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PHP has the function ucwords(), which allows for custom delimiters. This works well, and will turn my test string into My Test String no problem.
Take the following example: I want to make a super awesome 2009 gamer tag.
$gamerTag = 'xxx_l33t_xxx'; // Not yet epic.
echo ucwords($gamerTag,"x"); // want it to return 'xXx_l33t_xXx'
I would have assumed strings would delimit case-sensitively and update the the second x in each case, ignoring the third, since at that point the middle one would no longer match our delimiter.
However, this actually returns XxX_l33t_xXx, since it will automatically uppercase the first letter in the string.
I know that there are other methods of doing this (strsplit() array loops and pregreplace with a reverse lookup come to mind), but my primary question becomes the following:
Is there a way to delimit ucwords() such that it does not automatically uppercase the first character of the string?
The internal behaviour is unfortunately that the first character of the string will always be converted to upper case, regardless of the delimiters you pass in.
Digging into the PHP source, this is the implementation of ucwords:
*r = toupper((unsigned char) *r);
for (r_end = r + Z_STRLEN_P(return_value) - 1; r < r_end; ) {
if (mask[(unsigned char)*r++]) {
*r = toupper((unsigned char) *r);
}
}
From https://github.com/php/php-src/blob/master/ext/standard/string.c#L2651
Here r is the return value, and mask is a char array of the delimiting characters. The first call to toupper (outside the of the loop) means that there's no way to prevent the first character being converted.
Because this is done, it means the second character is not converted, since it's now preceded by X, not x. The third character is handled "correctly".
This can actually cause some strange cascading behaviour, since the return value is being iterated over while it's being modified:
php > echo ucwords('aaa', 'A');
AAA
The initial string doesn't contain the delimiting character anywhere, but the result is completely upper-case.
As mentioned in a comment, there's an open PHP bug to reflect this behaviour in the documentation here: https://bugs.php.net/bug.php?id=78393
I need to change the decimal separator in a given string that has numbers in it.
What RegEx code can ONLY select the thousands separator character in the string?
It need to only select, when there is number around it. For example only when 123,456 I need to select and replace ,
I'm converting English numbers into Persian (e.g: Hello 123 becomes Hello ۱۲۳). Now I need to replace the decimal separator with Persian version too. But I don't know how I can select it with regex. e.g. Hello 121,534 most become Hello ۱۲۱/۵۳۴
The character that needs to be replaced is , with /
Use a regular expression with lookarounds.
$new_string = preg_replace('/(?<=\d),(?=\d)/', '/', $string);
DEMO
(?<=\d) means there has to be a digit before the comma, (?=\d) means there has to be a digit after it. But since these are lookarounds, they're not included in the match, so they don't get replaced.
According to your question, the main problem you face is to convert the English number into the Persian.
In PHP there is a library available that can format and parse numbers according to the locale, you can find it in the class NumberFormatter which makes use of the Unicode Common Locale Data Repository (CLDR) to handle - in the end - all languages known to the world.
So converting a number 123,456 from en_UK (or en_US) to fa_IR is shown in this little example:
$string = '123,456';
$float = (new NumberFormatter('en_UK', NumberFormatter::DECIMAL))->parse($string);
var_dump(
(new NumberFormatter('fa_IR', NumberFormatter::DECIMAL))->format($float)
);
Output:
string(14) "۱۲۳٬۴۵۶"
(play with it on 3v4l.org)
Now this shows (somehow) how to convert the number. I'm not so firm with Persian, so please excuse if I used the wrong locale here. There might be options as well to tell which character to use for grouping, but for the moment for the example, it's just to show that conversion of the numbers is taken care of by existing libraries. You don't need to re-invent this, which is even a sort of miss-wording, this isn't anything a single person could do, or at least it would be sort of insane to do this alone.
So after clarifying on how to convert these numbers, question remains on how to do that on the whole text. Well, why not locate all the potential places looking for and then try to parse the match and if successful (and only if successful) convert it to the different locale.
Luckily the NumberFormatter::parse() method returns false if parsing did fail (there is even more error reporting in case you're interested in more details) so this is workable.
For regular expression matching it only needs a pattern which matches a number (largest match wins) and the replacement can be done by callback. In the following example the translation is done verbose so the actual parsing and formatting is more visible:
# some text
$buffer = <<<TEXT
it need to only select , when there is number around it. for example only
when 123,456 i need to select and replace "," I'm converting English
numbers into Persian (e.g: "Hello 123" becomes "Hello ۱۲۳"). now I need to
replace the Decimal separator with Persian version too. but I don't know how
I can select it with regex. e.g: "Hello 121,534" most become
"Hello ۱۲۱/۵۳۴" The character that needs to be replaced is , with /
TEXT;
# prepare formatters
$inFormat = new NumberFormatter('en_UK', NumberFormatter::DECIMAL);
$outFormat = new NumberFormatter('fa_IR', NumberFormatter::DECIMAL);
$bufferWithFarsiNumbers = preg_replace_callback(
'(\b[1-9]\d{0,2}(?:[ ,.]\d{3})*\b)u',
function (array $matches) use ($inFormat, $outFormat) {
[$number] = $matches;
$result = $inFormat->parse($number);
if (false === $result) {
return $number;
}
return sprintf("< %s (%.4f) = %s >", $number, $result, $outFormat->format($result));
},
$buffer
);
echo $bufferWithFarsiNumbers;
Output:
it need to only select , when there is number around it. for example only
when < 123,456 (123456.0000) = ۱۲۳٬۴۵۶ > i need to select and replace "," I'm converting English
numbers into Persian (e.g: "Hello < 123 (123.0000) = ۱۲۳ >" becomes "Hello ۱۲۳"). now I need to
replace the Decimal separator with Persian version too. but I don't know how
I can select it with regex. e.g: "Hello < 121,534 (121534.0000) = ۱۲۱٬۵۳۴ >" most become
"Hello ۱۲۱/۵۳۴" The character that needs to be replaced is , with /
Here the magic is just two bring the string parts into action with the number conversion by making use of preg_replace_callback with a regular expression pattern which should match the needs in your question but is relatively easy to refine as you define the whole number part and false positives are filtered thanks to the NumberFormatter class:
pattern for Unicode UTF-8 strings
|
(\b[1-9]\d{0,2}(?:[ ,.]\d{3})*\b)u
| | |
| grouping character |
| |
word boundary -----------------+
(play with it on regex101.com)
Edit:
To only match the same grouping character over multiple thousand blocks, a named reference can be created and referenced back to it for the repetition:
(\b[1-9]\d{0,2}(?:(?<grouping_char>[ ,.])\d{3}(?:(?&grouping_char)\d{3})*)?\b)u
(now this get's less easy to read, get it deciphered and play with it on regex101.com)
To finalize the answer, only the return clause needs to be condensed to return $outFormat->format($result); and the $outFormat NumberFormatter might need some more configuration but as it is available in the closure, this can be done when it is created.
(play with it on 3v4l.org)
I hope this is helpful and opens up a broader picture to not look for solutions only because hitting a wall (and only there). Regex alone most often is not the answer. I'm pretty sure there are regex-freaks which can give you a one-liner which is pretty stable, but the context of using it will not be very stable. However not saying there is only one answer. Instead bringing together different levels of doings (divide and conquer) allows to rely on a stable number conversion even if yet still unsure on how to regex-pattern an English number.
You can write a regex to capture numbers with thousand separator, and then aggregate the two numeric parts with the separator you want :
$text = "Hello, world, 121,534" ;
$pattern = "/([0-9]{1,3}),([0-9]{3})/" ;
$new_text = preg_replace($pattern, "$1X$2", $text); // replace comma per 'X', keep other groups intact.
echo $new_text ; // Hello, world, 121X534
In PHP you can do that using str_replace
$a="Hello 123,456";
echo str_replace(",", "X", $a);
This will return: Hello 123X456
i have a textarea box
<textarea>abc
d</textarea>
i post this to the php script.
in php script i have..:
$a = $_POST["a"];
$allowed_chars= 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789 .<>="';
$scan = strspn($a, $allowed_chars);
if ($scan < strlen($a)){
echo "not allowed char after the $scan : ". substr($a, $scan,1)
}
this will print this on the web browser:
not allowed char after the 3 :
obviously the new line is a problem.
i want to know what i can add to my
$allowed_chars
list. i tried adding
\\
( escaped forward? backward? slash )
it did not work.
after the
not allowed char after the 3 :
it is suppose to tell me the character causing the problem but it is simply empty.. showing nothing. how can it be designed so it can show the conflicting character ?
UPDATE
this does not work
$a = $_POST["a"];
$allowed_chars= 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789 .<>="\r\n';
$scan = strspn($a, $allowed_chars);
if ($scan < strlen($a)){
echo "not allowed char after the $scan : ". substr($a, $scan,1)
}
( added \r\n to the list )
update 2
this also does not work:
$allowed_chars='abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789 "\r\n"';
update 3
solution seems to be to first use php's nl2br() function on the "$input".
in that post
Escape Regex Newline
you can see that to make a new line char is : '\n'
so for regexp could be '\n'
and then you can add as \ as you tell before
expect help you
The problem with your script is that new line are multiple characters that define a distinct character. While you state \r\n that means you're on Windows and this code will also not work on a Linux server.
I'm not sure what you're trying to do but from the code I see its better to use Regex.
$s = 'some string I want to see the data on.';
$var = preg_match ( '/[A-z0-9].*/' , $s , $m);
print_r($m);
In this case it will only fetch the data before a line break which is also compatible with Linux.
This, unless you use the multi-line modifier in regex. Then you can check if the count($m) is greater then 1 it means it has multiple matches.
The regex [A-z0-9].* means match in range of A-Z & a-z & 0-9. Cause regex runs on a lower level then PHP (on the CPU) it is much more efficient at this task.
Regex is like a search code for a string, its extremely flexible and I would suggest you dive into the subject.
I'm just getting to know regular expressions, but after doing quite a bit of reading (and learning quite a lot), I still have not been able to figure out a good solution to this problem.
Let me be clear, I understand that this particular problem might be better solved not using regular expressions, but for the sake of brevity let me just say that I need to use regular expressions (trust me, I know there are better ways to solve this).
Here's the problem. I'm given a big file, each line of which is exactly 4 characters long.
This is a regex that defines "valid" lines:
"/^[AB][CD][EF][GH]$/m"
In english, each line has either A or B at position 0, either C or D at position 1, either E or F at position 2, and either G or H at position 3. I can assume that each line will be exactly 4 characters long.
What I'm trying to do is given one of those lines, match all other lines that contain 2 or more common characters.
The below example assumes the following:
$line is always a valid format
BigFileOfLines.txt contains only valid lines
Example:
// Matches all other lines in string that share 2 or more characters in common
// with "$line"
function findMatchingLines($line, $subject) {
$regex = "magic regex I'm looking for here";
$matchingLines = array();
preg_match_all($regex, $subject, $matchingLines);
return $matchingLines;
}
// Example Usage
$fileContents = file_get_contents("BigFileOfLines.txt");
$matchingLines = findMatchingLines("ACFG", $fileContents);
/*
* Desired return value (Note: this is an example set, there
* could be more or less than this)
*
* BCEG
* ADFG
* BCFG
* BDFG
*/
One way I know that will work is to have a regex like the following (the following regex would only work for "ACFG":
"/^(?:AC.{2}|.CF.|.{2}FG|A.F.|A.{2}G|.C.G)$/m"
This works alright, performance is acceptable. What bothers me about it though is that I have to generate this based off of $line, where I'd rather have it be ignorant of what the specific parameter is. Also, this solution doesn't scale terrible well if later the code is modified to match say, 3 or more characters, or if the size of each line grows from 4 to 16.
It just feels like there's something remarkably simple that I'm overlooking. Also seems like this could be a duplicate question, but none of the other questions I've looked at really seem to address this particular problem.
Thanks in advance!
Update:
It seems that the norm with Regex answers is for SO users to simply post a regular expression and say "This should work for you."
I think that's kind of a halfway answer. I really want to understand the regular expression, so if you can include in your answer a thorough (within reason) explanation of why that regular expression:
A. Works
B. Is the most efficient (I feel there are a sufficient number of assumptions that can be made about the subject string that a fair amount of optimization can be done).
Of course, if you give an answer that works, and nobody else posts the answer *with* a solution, I'll mark it as the answer :)
Update 2:
Thank you all for the great responses, a lot of helpful information, and a lot of you had valid solutions. I chose the answer I did because after running performance tests, it was the best solution, averaging equal runtimes with the other solutions.
The reasons I favor this answer:
The regular expression given provides excellent scalability for longer lines
The regular expression looks a lot cleaner, and is easier for mere mortals such as myself to interpret.
However, a lot of credit goes to the below answers as well for being very thorough in explaining why their solution is the best. If you've come across this question because it's something you're trying to figure out, please give them all a read, helped me tremendously.
Why don't you just use this regex $regex = "/.*[$line].*[$line].*/m";?
For your example, that translates to $regex = "/.*[ACFG].*[ACFG].*/m";
This is a regex that defines "valid" lines:
/^[A|B]{1}|[C|D]{1}|[E|F]{1}|[G|H]{1}$/m
In english, each line has either A or B at position 0, either C or D
at position 1, either E or F at position 2, and either G or H at
position 3. I can assume that each line will be exactly 4 characters
long.
That's not what that regex means. That regex means that each line has either A or B or a pipe at position 0, C or D or a pipe at position 1, etc; [A|B] means "either 'A' or '|' or 'B'". The '|' only means 'or' outside of character classes.
Also, {1} is a no-op; lacking any quantifier, everything has to appear exactly once. So a correct regex for the above English is this:
/^[AB][CD][EF][GH]$/
or, alternatively:
/^(A|B)(C|D)(E|F)(G|H)$/
That second one has the side effect of capturing the letter in each position, so that the first captured group will tell you whether the first character was A or B, and so on. If you don't want the capturing, you can use non-capture grouping:
/^(?:A|B)(?:C|D)(?:E|F)(?:G|H)$/
But the character-class version is by far the usual way of writing this.
As to your problem, it is ill-suited to regular expressions; by the time you deconstruct the string, stick it back together in the appropriate regex syntax, compile the regex, and do the test, you would probably have been much better off just doing a character-by-character comparison.
I would rewrite your "ACFG" regex thus: /^(?:AC|A.F|A..G|.CF|.C.G|..FG)$/, but that's just appearance; I can't think of a better solution using regex. (Although as Mike Ryan indicated, it would be better still as /^(?:A(?:C|.E|..G))|(?:.C(?:E|.G))|(?:..EG)$/ - but that's still the same solution, just in a more efficiently-processed form.)
You've already answered how to do it with a regex, and noted its shortcomings and inability to scale, so I don't think there's any need to flog the dead horse. Instead, here's a way that'll work without the need for a regex:
function findMatchingLines($line) {
static $file = null;
if( !$file) $file = file("BigFileOfLines.txt");
$search = str_split($line);
foreach($file as $l) {
$test = str_split($l);
$matches = count(array_intersect($search,$test));
if( $matches > 2) // define number of matches required here - optionally make it an argument
return true;
}
// no matches
return false;
}
There are 6 possibilities that at least two characters match out of 4: MM.., M.M., M..M, .MM., .M.M, and ..MM ("M" meaning a match and "." meaning a non-match).
So, you need only to convert your input into a regex that matches any of those possibilities. For an input of ACFG, you would use this:
"/^(AC..|A.F.|A..G|.CF.|.C.G|..FG)$/m"
This, of course, is the conclusion you're already at--so good so far.
The key issue is that Regex isn't a language for comparing two strings, it's a language for comparing a string to a pattern. Thus, either your comparison string must be part of the pattern (which you've already found), or it must be part of the input. The latter method would allow you to use a general-purpose match, but does require you to mangle your input.
function findMatchingLines($line, $subject) {
$regex = "/(?<=^([AB])([CD])([EF])([GH])[.\n]+)"
+ "(\1\2..|\1.\3.|\1..\4|.\2\3.|.\2.\4|..\3\4)/m";
$matchingLines = array();
preg_match_all($regex, $line + "\n" + $subject, $matchingLines);
return $matchingLines;
}
What this function does is pre-pend your input string with the line you want to match against, then uses a pattern that compares each line after the first line (that's the + after [.\n] working) back to the first line's 4 characters.
If you also want to validate those matching lines against the "rules", just replace the . in each pattern to the appropriate character class (\1\2[EF][GH], etc.).
People may be confused by your first regex. You give:
"/^[A|B]{1}|[C|D]{1}|[E|F]{1}|[G|H]{1}$/m"
And then say:
In english, each line has either A or B at position 0, either C or D at position 1, either E or F at position 2, and either G or H at position 3. I can assume that each line will be exactly 4 characters long.
But that's not what that regex means at all.
This is because the | operator has the highest precedence here. So, what that regex really says, in English, is: Either A or | or B in the first position, OR C or | or D in the first position, OR E or | or F in the first position, OR G or '|orH` in the first position.
This is because [A|B] means a character class with one of the three given characters (including the |. And because {1} means one character (it is also completely superfluous and could be dropped), and because the outer | alternate between everything around it. In my English expression above each capitalized OR stands for one of your alternating |'s. (And I started counting positions at 1, not 0 -- I didn't feel like typing the 0th position.)
To get your English description as a regex, you would want:
/^[AB][CD][EF][GH]$/
The regex will go through and check the first position for A or B (in the character class), then check C or D in the next position, etc.
--
EDIT:
You want to test for only two of these four characters matching.
Very Strictly speaking, and picking up from #Mark Reed's answer, the fastest regex (after it's been parsed) is likely to be:
/^(A(C|.E|..G))|(.C(E)|(.G))|(..EG)$/
as compared to:
/^(AC|A.E|A..G|.CE|.C.G|..EG)$/
This is because of how the regex implementation steps through text. You first test if A is in the first position. If that succeeds, then you test the sub-cases. If that fails, then you're done with all those possible cases (or which there are 3). If you don't yet have a match, you then test if C is in the 2nd position. If that succeeds, then you test for the two subcases. And if none of those succeed, you test, `EG in the 3rd and 4th positions.
This regex is specifically created to fail as fast as possible. Listing each case out separately, means to fail, you would have test 6 different cases (each of the six alternatives), instead of 3 cases (at a minimum). And in cases of A not being the first position, you would immediately go to test the 2nd position, without hitting it two more times. Etc.
(Note that I don't know exactly how PHP compiles regex's -- it's possible that they compile to the same internal representation, though I suspect not.)
--
EDIT: On additional point. Fastest regex is a somewhat ambiguous term. Fastest to fail? Fastest to succeed? And given what possible range of sample data of succeeding and failing rows? All of these would have to be clarified to really determine what criteria you mean by fastest.
Here's something that uses Levenshtein distance instead of regex and should be extensible enough for your requirements:
$lines = array_map('rtrim', file('file.txt')); // load file into array removing \n
$common = 2; // number of common characters required
$match = 'ACFG'; // string to match
$matchingLines = array_filter($lines, function ($line) use ($common, $match) {
// error checking here if necessary - $line and $match must be same length
return (levenshtein($line, $match) <= (strlen($line) - $common));
});
var_dump($matchingLines);
I bookmarked the question yesterday in the evening to post an answer today, but seems that I'm a little late ^^ Here is my solution anyways:
/^[^ACFG]*+(?:[ACFG][^ACFG]*+){2}$/m
It looks for two occurrences of one of the ACFG characters surrounded by any other characters. The loop is unrolled and uses possessive quantifiers, to improve performance a bit.
Can be generated using:
function getRegexMatchingNCharactersOfLine($line, $num) {
return "/^[^$line]*+(?:[$line][^$line]*+){$num}$/m";
}
So I have an interesting problem: I have a string, and for the most part i know what to expect:
http://www.someurl.com/st=????????
Except in this case, the ?'s are either upper case letters or numbers. The problem is, the string has garbage mixed in: the string is broken up into 5 or 6 pieces, and in between there's lots of junk: unprintable characters, foreign characters, as well as plain old normal characters. In short, stuff that's apt to look like this: Nyþ=mî;ëMÝ×nüqÏ
Usually the last 8 characters (the ?'s) are together right at the end, so at the moment I just have PHP grab the last 8 chars and hope for the best. Occasionally, that doesn't work, so I need a more robust solution.
The problem is technically unsolvable, but I think the best solution is to grab characters from the end of the string while they are upper case or numeric. If I get 8 or more, assume that is correct. Otherwise, find the st= and grab characters going forward as many as I need to fill up the 8 character quota. Is there a regex way to do this or will i need to roll up my sleeves and go nested-loop style?
update:
To clear up some confusion, I get an input string that's like this:
[garbage]http:/[garbage]/somewe[garbage]bsite.co[garbage]m/something=[garbage]????????
except the garbage is in unpredictable locations in the string (except the end is never garbage), and has unpredictable length (at least, I have been able to find patterns in neither). Usually the ?s are all together hence me just grabbing the last 8 chars, but sometimes they aren't which results in some missing data and returned garbage :-\
$var = '†http://þ=www.ex;üßample-website.î;ëcomÝ×ü/joy_hÏere.html'; // test case
$clean = join(
array_filter(
str_split($var, 1),
function ($char) {
return (
array_key_exists(
$char,
array_flip(array_merge(
range('A','Z'),
range('a','z'),
range((string)'0',(string)'9'),
array(':','.','/','-','_')
))
)
);
}
)
);
Hah, that was a joke. Here's a regex for you:
$clean = preg_replace('/[^A-Za-z0-9:.\/_-]/','',$var);
As stated, the problem is unsolvable. If the garbage can contain "plain old normal characters" characters, and the garbage can fall at the end of the string, then you cannot know whether the target string from this sample is "ABCDEFGH" or "BCDEFGHI":
__http:/____/somewe___bsite.co____m/something=__ABCDEFGHI__
What do these values represent? If you want to retain all of it, just without having to deal with garbage in your database, maybe you should hex-encode it using bin2hex().
You can use this regular expression :
if (preg_match('/[\'^£$%&*()}{##~?><>,|=_+¬-]/', $string) ==1)