In the process of writing a custom little template engine I want to match a block like
{foreach foo as bar}
{bar.name}
{endforeach}
//with regex
preg_match_all('/{(?!{)([\w\s]+)}(?!})(.*?){(?!{)(\w+)}(?!})/us', $string, $matches, PREG_SET_ORDER)
So the first group must have alnum and whitespace chars with [\w\s]+
the negative lookahead (?!{) is to not allow blocks that start with {{
//so a block like
{{foreach bla as bla}}
//would not be matched.
The problem is that this regex also matches {var} without whitespace.
And this is what I dont understand due to my first class definition
of [\w\s]+
To match at least 2 word char sequences separated with at least 1 whitespace, and allow leading and trailing whitespaces, you may use
\s*\w+(?:\s+\w+)+\s*
In details:
\s* - 0+ whitespaces
\w+ - 1 or more word chars
(?: - start of a non-capturing group that is used for grouping subpattern sequences*:
\s+ - 1 or more whitespaces
\w+ - 1 or more word chars
)+ - 1 or more occurrences of the group
\s* - trailing 0+ whitespace chars.
The entire regex will look like
{(?!{)(\s*\w+(?:\s+\w+)+\s*)}(?!})(.*?){(?!{)(\w+)}(?!})
See the updated regex demo
Related
Using PHP8, I'm struggling to figure out how to conditionally match some key that may or may not appear in a string.
I would like to match both
-----------key=xyz---------------
AND
--------------------------
The dashes("-") could be any non-space character, and only used here for a cleaner to read example.
The regex is matching "key=..." if its containing group is greedy like below.
But this isn't adequate, because the full match will fail a "key=xyz" is missing the subject string.
/
(\S*)?
(key\=(?<foundkey>[[:alnum:]-]*))
\S*
/x
if that capture group is non-greedy, then the regex just ignores the key match any "key=xyz"
/
(\S*)?
(key\=(?<foundkey>[[:alnum:]-]*))?
\S*
/x
I tried debugging in this regex101 example but couldn't figure it out.
I sorted this out using multiple regexs, but hoping someone can help address my misunderstandings so I learn know how to make this work as a single regex.
Thanks
You may use:
/
^
\S*?
(?:
key=(?<foundkey>\w+)
\S*
)?
$
/xm
RegEx Demo
RegEx Breakdown:
^: Start
\S*?: Match 0 or more whitespaces non-greedy
(?:: Start Lookahead
key=(?<foundkey>\w+): Match key= text followed by 1+ word characters as capture group foundkey
\S*: Match 0 or more whitespaces
)?: End lookahead. ? makes it an optional match
$; End
I'm trying to evaluate a multiline RegExp with preg_match_all.
Unfortunately there seems to be a character limit around 24,000 characters (24,577 to be specific).
Does anyone know how to get this to work?
Pseudo-code:
<?php
$data = 'TRACE: aaaa(24,577 characters)';
preg_match_all('/([A-Z]+): ((?:(?![A-Z]+:).)*)\n/s', $data, $matches);
var_dump($matches);
?>
Working example (with < 24,577 characters): https://3v4l.org/8iRCc
Example that's NOT working (with > 24,577 characters): https://3v4l.org/ceKn6
You might rewrite the pattern using a negated character class instead of the tempered greedy token approach with the negative lookahead:
([A-Z]+): ([^A-Z\r\n]*(?>(?:\r?\n|[A-Z](?![A-Z]*:))[^A-Z\r\n]*)*)\r?\n
([A-Z]+): Capture group 1, match 1+ uppercase chars : and a space
( Capture group 2
[^A-Z\r\n]* Match 1+ times any char except A-Z or a newline
(?> Atomic group
(?: Non capture group
\r?\n Match a newline
| Or
[A-Z] Match a char other than A-Z
(?![A-Z]*:) Negative lookahead, assert not optional chars A-Z and :
) Close non capture group
[^A-Z\r\n]* Optionally match any char except A-Z
)* Close atomic group and optionally repeat
)\r?\n Close group 2 and match a newline
Regex demo | Php demo
If the TRACE: is at the start of the string, you can also add an anchor:
^([A-Z]+): ([^A-Z\r\n]*(?>(?:\r?\n|[A-Z](?![A-Z]*:))[^A-Z\r\n]*)*)\r?\n
Regex demo
Edit
If the strings start with the same format, you can capture and match all lines that do not start with the opening format.
^([A-Z]+): (.*(?:\r?\n(?![A-Z]+: ).*)*)
The pattern matches:
^ Start of string
([A-Z]+): Capture group 1
( Capture group 2
.* Match the rest of the line
(?:\r?\n(?![A-Z]+: ).*)* Repeat matching all lines that do not start with the pattern [A-Z]+:
) Close group 2
Regex demo
In php you can use
$re = '/^([A-Z]+): (.*(?:\r?\n(?![A-Z]+: ).*)*)/m';
Php demo
Try this
preg_match('/\A(?>[^\r\n]*(?>\r\n?|\n)){0,4}[^\r\n]*\z/',$data)
I need to match a series of strings that:
Contain at least 3 numbers
0 or more letters
0 or 1 - (not more)
0 or 1 \ (not more)
These characters can be in any position in the string.
The regular expression I have so far is:
([A-Z0-9]*[0-9]{3,}[\/]?[\-]?[0-9]*[A-Z]*)
This matches the following data in the following cases. The only one that does not match is the first one:
02ABU-D9435
013DFC
1123451
03323456782
ADS7124536768
03SDFA9433/0
03SDFA9433/
03SDFA9433/1
A41B03423523
O4AGFC4430
I think perhaps I am being too prescriptive about positioning. How can I update this regex to match all possibilities?
PHP PCRE
The following would not match:
01/01/2018 [multiple / or -]
AA-AA [no numbers]
Thanks
One option could be using lookaheads to assert 3 digits, not 2 backslashes and not 2 times a hyphen.
(?<!\S)(?=(?:[^\d\s]*\d){3})(?!(?:[^\s-]*-){2})(?!(?:[^\s\\]*\\){2})[A-Z0-9/\\-]+(?!\S)
About the pattern
(?<!\S) Assert what is on the left is not a non whitespace char
(?=(?:[^\d\s]*\d){3}) Assert wat is on the right is 3 times a whitespace char or digit
(?!(?:[^\s-]*-){2}) Assert what is on the right is not 2 times a whitespace char a hyphen
(?!(?:[^\s\\]*\\){2}) Assert what is on the right is not 2 times a whitespace char a backslash
[A-Z0-9/\\-]+ Match any of the listed 1+ times
(?!\S) Assert what is on the right is not a non whitespace char
Regex demo
Your patterns can be checked with positive/negative lookaheads anchored at the start of the string:
at least 3 digits -> find (not necessarily consecutive) 3 digits
no more than 1 '-' -> assert absence of (not necessarily consecutive) 2 '-' characters
no more than 1 '/' -> assert absence of (not necessarily consecutive) 2 '/' characters
0 or more letters -> no check needed.
If these conditions are met, any content is permitted.
The regex implementing this:
^(?=(([^0-9\r\n]*\d){3}))(?!(.*-){2})(?!(.*\/){2}).*$
Check out this Regex101 demo.
Remark
This solution assumes that each string tested resides on its own line, ie. not just being separated by whitespace.
In case the strings are separated by whitespace, choose the solution of user #TheFourthBird (which essentially is the same as this one but caters for the whitespace separation)
You can test the condition for both the hyphen and the slash into a same lookahead using a capture group and a backreference:
~\A(?!.*([-/]).*\1)(?:[A-Z/-]*\d){3,}[A-Z/-]*\z~
demo
detailled:
~ # using the tild as pattern delimiter avoids to escape all slashes in the pattern
\A # start of the string
(?! .* ([-/]) .* \1 ) # negative lookahead:
# check that there's no more than one hyphen and one slash
(?: [A-Z/-]* \d ){3,} # at least 3 digits
[A-Z/-]* # eventual other characters until the end of the string
\z # end of the string.
~
To better understand (if you are not familiar with): these three subpatterns start from the same position (in this case the beginning of the string):
\A
(?! .* ([-/]) .* \1 )
(?: [A-Z/-]* \d ){3,}
This is possible only because the two first are zero-width assertions that are simple tests and don't consume any character.
We are extracting text from PDF files, and there is a high frequency of results that contain malformed text. Specifically adding spaces between the characters of a word. e.g. SEATTLE is being returned as S E A T T L E.
Is there a RegEx expression for preg_replace that can remove any spaces in the case of n number of single character "words"? Specifically, remove spaces from any occurrence of a string that is more than 3 single alpha characters and is separated by spaces?
If googled this for awhile, but can't even imagine how to construct the expression. As expressed in a comment, I don't want ALL spaces removed, but only when there is an occurrence of >3 single alpha characters, e.g. Welcome to the Greater S E A T T L E area should become Welcome to the Greater SEATTLE area. The result is to be used in full text searching, so case sensitivity is not a concern.
You may use a simple approach with a preg_replace_callback. Match '~\b[A-Za-z](?: [A-Za-z]){2,}\b~' and str_replace spaces in the anonymous function:
$regex = '~\b[A-Za-z](?: [A-Za-z]){2,}\b~';
$result = preg_replace_callback($regex, function($m) {
return str_replace(" ", "", $m[0]);
}, $s);
See the regex demo.
To only match sequences of uppercase letters, remove a-z from the pattern:
$regex = '~\b[A-Z](?: [A-Z]){2,}\b~';
And another thing: there may be soft/hard spaces, tabs, other kind of whitespace. Then, use
$regex = '~\b[A-Za-z](?:\h[A-Za-z]){2,}\b~u';
^^ ^
Finally, to match any Unicode letter, use \p{L} (to only match uppercase ones, \p{Lu}) instead of [a-zA-Z]:
$regex = '~\b\p{L}(?:\h\p{L}){2,}\b~u';
NOTE: It will most probably fail to work in some cases, e.g. when there are one-letter words. You will have to handle those cases separately/manually. Anyway, there is no safe regex-only way to fix OCR issues.
Pattern details
\b - a word boundary
[A-Za-z] - a single letter
(?: [A-Za-z]){2,} - 2 or more occurrences of
- a space (\h matches any kind of horizontal whitespace)
[A-Za-z] - a single letter
\b - a word boundary
When usign u modifier, \h becomes Unicode-aware.
You could do this in one go:
(?i:(?<!\S)([a-z]) +((?1))|\G(?!\A) +((?1))\b)
See live demo here
Explanation:
(?i: # Start of non-capturing group with case-insensitive modifier on
(?<!\S) # Negative lookbehind to ensure there is no leading non-whitespace character
([a-z]) + # Capture one letter and at least one space
((?1)) # Capture one letter in 2nd capturing group
| # Or
\G(?!\A) + # Start match from where previous match ends
# with matching spaces
((?1))\b # Match a letter at word boundary
) # End of non-capturing group
PHP code:
$str = preg_replace('~(?i:(?<!\S)([a-z]) +((?1))|\G(?!\A) +((?1))\b)~', '$1$2$3', $str);
You may use this pure regex approach with lookarounds and \G:
$re = '~\b(?:(?=(?:\pL\h+){3}\pL\b)|(?<!^)\G)(\pL)\h+(?=\pL\b)~';
$repl = preg_replace($re, '$1', $str);
RegEx Demo
RegEx Details:
\b: Match word boundary
(?:: Start non-capture group
(?=(?:\pL\h+){3}\pL\b): Lookahead to assert we have 3+ single letters separated by 1+ spaces
|: OR
(?<!^)\G: \G asserts position at the end of the previous match. (?<!^) ensures we don't match start of the string for the first match
): End non-capture group
(\pL): Match a single letter and capture it
\h+: Followed by 1+ horizontal whitespace
(?=\pL\b): Assert that we only have a single letter ahead
In the replacement we use $1 which is the letter left of whitespace we capture
I am a serious newbie with regular expression so please disregard my mistakes. I need to be sure that several criteria in a string are met.
Requirements:
Have at most 5 words
Max of 256 characters
Word is considered 1 or more characters - no spaces
Shouldn't contain two consecutive spaces
Example:
Tree blows in the wind
1-Tree falls over
Failure Example:
Tree blows in the night sky
Tree breaks 2 limbs during night
Can this be done in one single expression or should it be broken up?
Validating for 2 spaces:
- /^\s\s$/
Max of 256 characters:
- /^[a-zA-Z0-9]{,256}$/
I am not sure how to test case for the 5 words and combine the other criteria that I impose. Can anyone help?
Test for word:
- /^\w{1,5}$
You can try this:
(?s)\A(?!.{257}|.*\s\s)\W*\w*(?:\W+\w+){0,4}\W*\z
pattern details:
(?s) # turn on the singleline mode: allow the dot to match newlines
\A # start of the string anchor
(?! # open a negative lookahead assertion: means not followed by
.{257} # 257 characters
| # OR
.*\s\s # two consecutive whitespaces
) # close the negative lookahead
\W* # optional non-word characters
\w* # optional word characters (nothing in your requirements forbids to have a string without words or an empty string)
(?: # open a non-capturing group
\W+ # non-word characters: words are obviously separated with non-word characters
\w+ # an other word
){0,4} # repeat the non-capturing group between zero and 4 times
\W* # optional non-word characters
\z # anchor for the end of the string