I'm stuck writing a preg_match
I have a string:
XPMG_ar121023.txt
and need to extract the 2 letters between XPMG_ and the first digit - be it a 0-9
$str = 'XPMG_ar121023.txt';
preg_match('/('XPMG_')|[0-9\,]))/', $str, $match);
print_r($match);
Maybe this isn't the best option: My characters will always be
You can just do
$str = "XPMG_ar121023.txt" ;
preg_match('/_([a-z]+)/i', $str, $match);
var_dump($match[1]);
Output
string 'ar' (length=2)
This is too simple for a regular expression. Just $match = substr($str,5,3) would get what you're asking for.
Let me walk through this step by step so as to help you solve similar problems in the future. Suppose we have the following format for our filenames:
XPMG_ar121023.txt
We know what we want to capture, we want the "ar" right after the _ and just before the numbers begin. So our expression would look something like this:
_[a-z]+
This is pretty straight-forward. We're starting by looking for an underscore, followed by any number of letters between a and z. The square brackets define a character class. Our class consists of the alphabet, but you can push specific numbers in there and more if you like.
Now because we want to capture only the letters, we need to put parenthesis around that part of the pattern:
_([a-z]+)
In the result we will now have access to only that subpattern. Next we put our delimiters in place to specify where our pattern begins, and ends:
/_([a-z]+)/
And lastly, after our closing delimiter we can add some modifiers. As it is written, our pattern only looks for lower-case letters. We can add the i modifier to make this case-insensitive:
/_([a-z]+)/i
Voila, we're done. Now we can pass it into preg_match to see what it spits out:
preg_match( "/_([a-z]+)/i", "XPMG_ar121023.txt", $match );
This function takes a pattern as the first parameter, a string to match it against as the second, and lastly a variable to spit the results into. When all is said and done, we can check $match for our data.
The results of this operation follow:
array(2) {
[0]=> string(3) "_ar"
[1]=> string(2) "ar"
}
This is the contents of $match. Notice our full pattern is found in the first index of the array, and our captured portion is provided in the second index of the array.
echo $match[1]; // ar
Hope this helps.
Well, why not:
$letters = $str[5].$str[6];
:)
After all, you'll always need the 2 chars after the fixed prefix, there are many ways that do not require a regexp (substr() being the best anyway)
Related
I have a string that contains something like "LAB_FF, LAB_FF12" and I'm trying to use preg_replace to look for both patterns and replace them with different strings using a pattern match of;
/LAB_[0-9A-F]{2}|LAB_[0-9A-F]{4}/
So input would be
LAB_FF, LAB_FF12
and the output would need to be
DAB_FF, HAD_FF12
Problem is, for the second string, it interprets it as "LAB_FF" instead of "LAB_FF12" and so the output is
DAB_FF, DAB_FF
I've tried splitting the input line out using 2 different preg_match statements, the first looking for the {2} pattern and the second looking for the {4} pattern. This sort of works in that I can get the correct output into 2 separate strings but then can't combine the two strings to give the single amended output.
\b is word boundary. Meaning it will look at where the word ends and not only pattern match.
https://regex101.com/r/upY0gn/1
$pattern = "/\bLAB_[0-9A-F]{2}\b|\bLAB_[0-9A-F]{4}\b/";
Seeing the comment on the other answer about how to replace the string.
This is one way.
The pattern will create empty entries in the output array for each pattern that fails.
In this case one (the first).
Then it's just a matter of substr.
$re = '/(\bLAB_[0-9A-F]{2}\b)|(\bLAB_[0-9A-F]{4}\b)/';
$str = 'LAB_FF12';
preg_match($re, $str, $matches);
var_dump($matches);
$substitutes = ["", "DAB", "HAD"];
For($i=1; $i<count($matches); $i++){
If($matches[$i] != ""){
$result = $substitutes[$i] . substr($matches[$i],3);
Break;
}
}
Echo $result;
https://3v4l.org/gRvHv
You can specify exact amounts in one set of curly braces, e.g. `{2,4}.
Just tested this and seems to work:
/LAB_[0-9A-F]{2,4}/
LAB_FF, LAB_FFF, LAB_FFFF
EDIT: My mistake, that actually matches between 2 and 4. If you change the order of your selections it matches the first it comes to, e.g.
/LAB_([0-9A-F]{4}|[0-9A-F]{2})/
LAB_FF, LAB_FFFF
EDIT2: The following will match LAB_even_amount_of_characters:
/LAB_([0-9A-F]{2})+/
LAB_FF, LAB_FFFF, LAB_FFFFFF...
I have the following the following string:
"#(admin/pages|admin/pages/add|admin/pages/[0-9]+)#"
And this string to compare it to:
"admin/pages/1"
What I need is to return "admin/pages/1" when comparing the 2 strings using preg_match(). I have the following code and it's not working:
if(preg_match("#(admin/pages|admin/pages/add|admin/pages/[0-9]+)#", "admin/pages/1", $matches) {
var_dump($matches);
}
This is the output i get:
array(2) { [0]=> string(11) "admin/pages" [1]=> string(11) "admin/pages" }
Can anybody help out?
Use the following short regex parrent:
"#admin/pages(/add|/[0-9]+)?#"
(/add|/[0-9]+)? - optional alternative group, matches either /add or /<number> at the end of searched substring if occurs
Change your regex to:
"#(admin/pages(?:/\d+)?|admin/pages/add)#"
You don't need both variants (admin/pages|admin/pages/[0+9]+) if you put the digits in the first pattern and make them optional.
Question marks and repetitions are greedy by default, that's why it will always include the digits in the match for my version.
On the other hand, if you have an alternation, it will always pick the first match. Since your first alternation does not include digits, they are not matched.
If you're also wondering why you get your match two times, that's because of the way preg_match works.
Quote from the documentation:
$matches[0] will contain the text that matched the full pattern,
$matches[1] will have the text that matched the first captured
parenthesized subpattern, and so on.
You can remove the outer parentheses if the whole match is enough:
"#admin/pages(?:/\d+)?|admin/pages/add#"
Just use $matches[0].
And, as #RomanPerekhrest has written and I shamelessly include in this answer, you can shorten your pattern. You don't need to include admin/pages multiple times:
"#admin/pages(?:/add|/\d+)?#"
Try changing the order of components:
"#(admin/pages/[0-9]+|admin/pages/add|admin/pages)#"
The regular expression is satisfied as soon as something matches. In your case, it stopped as soon as it found admin/pages without looking any further.
Using a regular expression I want to move two letters in a string.
W28
L36
W29-L32
Should be changed to:
28W
36L
29W-32L
The numbers vary between 25 and 44. The letters that need to be moved are always "W" and/or "L" and the "W" is always first when they both exist in the string.
I need to do this with a single regular expression using PHP. Any ideas would be awesome!
EDIT:
I'm new to regular expressions and tried a lot of things without success. The closest I came was using "/\b(W34)\b/" for each possibility. I also found something about using variables in the replace function but had no luck using these.
Your regex \b(W34)\b matches exactly W34 as a whole word. You need a character class to match W or L, and some alternatives to match the numeric range, and use the most of capturing groups.
You can use the following regex replacement:
$re = '/\b([WL])(2[5-9]|3[0-9]|4[0-4])\b/';
$str = "W28\nL36\nW29-L32";
$result = preg_replace($re, "$2$1", $str);
echo $result;
See IDEONE demo
Here, ([WL]) matches and captures either W or L into group 1, and (2[5-9]|3[0-9]|4[0-4]) matches integer numbers from 25 till 44 and captures into group 2. Backreferences are used to reverse the order of the groups in the replacement string.
And here is a regex demo in case you want to adjust it later.
I need help extracing all the sub string between curly brackets that are found inside a specific string.
I found some solutions in javascript but I need it for PHP.
$string = "www.example.com/?foo={foo}&test={test}";
$subStrings = HELPME($string);
print_r($subStrings);
The result should be:
array( [0] => foo, [1] => test )
I tried playing with preg_match but I got confused.
I'd appreciate if whoever manage to get it to work with preg_match, explain also what is the logic behind it.
You could use this regex to capture the strings between {}
\{([^}]*)\}
Explanation:
\{ Matches a literal {
([^}]*) Capture all the characters not of } zero or more times. So it would capture upto the next } symbol.
\} Matches a literal }
Your code would be,
<?php
$regex = '~\{([^}]*)\}~';
$string = "www.example.com/?foo={foo}&test={test}";
preg_match_all($regex, $string, $matches);
var_dump($matches[1]);
?>
Output:
array(2) {
[0]=>
string(3) "foo"
[1]=>
string(4) "test"
}
DEMO
Regex Pattern: \{(\w+)\}
Get all the matches that is captured by parenthesis (). The pattern says anything that is enclosed by {...} are captured.
Sample code:
$regex = '/\{(\w{1,})\}/';
$testString = ''; // Fill this in
preg_match_all($regex, $testString, $matches);
// the $matches variable contains the list of matches
Here is demo on debuggex
If you want to capture any type of character inside the {...} then try below regex pattern.
Regex : \{(.*?)\}
Sample code:
$regex = '/\{(.{0,}?)\}/';
$testString = ''; // Fill this in
preg_match_all($regex, $testString, $matches);
// the $matches variable contains the list of matches
Here is demo on debuggex
<?php
$string = "www.example.com/?foo={foo}&test={test}";
$found = preg_match('/\{([^}]*)\}/',$string, $subStrings);
if($found){
print_r($subStrings);
}else{
echo 'NOPE !!';
}
DEMO HERE
Function parse_url, which parses a URL and return its components. Including the query string.
Try This:
preg_match_all("/\{.*?\}/", $string, $subStrings);
var_dump($subStrings[0]);
Good Luck!
You can use the expression (?<=\{).*?(?=\}) to match any string of text enclosed in {}.
$string = "www.example.com/?foo={foo}&test={test}";
preg_match_all("/(?<=\{).*?(?=\})/",$string,$matches);
print_r($matches[0]);
Regex explained:
(?<=\{) is a positive lookbehind, asserting that the line of text is preceeded by a {.
Similarly (?=\}) is a positive lookahead asserting that it is followed by a }. .* matches 0 or more characters of any type. And the ? in .*? makes it match the least possible amount of characters. (Meaning it matches foo in {foo} and {bar} as opposed to foo} and {bar.
$matches[0] contains an array of all the matched strings.
I see answers here using regular expressions with capture groups, lookarounds, and lazy quantifiers. All of these techniques will slow down the pattern -- granted, the performance is very unlikely to be noticeable in the majority of use cases. Because we are meant to offer solutions that are suitable to more scenarios than just the posted question, I'll offer a few solutions that deliver the expected result and explain the differences using the OP's www.example.com/?foo={foo}&test={test} string assigned to $url. I have prepared a php DEMO of the techniques to follow. For information about the function calls, please follow the links to the php manual. For an in depth breakdown of the regex patterns, I recommend using regex101.com -- a free online tool that allows you to test patterns against strings, see the results as both highlighted text and a grouped list, and provides a technique breakdown character-by-character of how the regex engine is interpreting your pattern.
#1 Because your input string is a url, a non-regex technique is appropriate because php has native functions to parse it: parse_url() with parse_str(). Unfortunately, your requirements go beyond extracting the query string's values, you also wish to re-index the array and remove the curly braces from the values.
parse_str(parse_url($url, PHP_URL_QUERY), $assocArray);
$values = array_map(function($v) {return trim($v, '{}');}, array_values($assocArray));
var_export($values);
While this approach is deliberate and makes fair use of native functions that were built for these jobs, it ends up making longer, more convoluted code which is somewhat unpleasant in terms of readability. Nonetheless, it provides the desired output array and should be considered as a viable process.
#2 preg_match_all() is a super brief and highly efficient technique to extract the values. One draw back with using regular expressions is that the regex engine is completely "unaware" of any special meanings that a formatted input string may have. In this case, I don't see any negative impacts, but when hiccups do arise, often the solution is to use a parser that is "format/data-type aware".
var_export(preg_match_all('~\{\K[^}]*~', $url, $matches) ? $matches[0] : []);
Notice that my pattern does not need capture groups or lookarounds; nor does my answer suffer from the use of a lazy quantifier. \K is used to "restart the fullstring match" (in other words, forget any matched characters upto that point). All of these features will mean that the regex engine can traverse the string with peak efficiency. If there is a downsides to using the function they are:
that a multi-dimensional array is generated while you only want a one-dimensional array
that the function creates a reference variable instead of returning the results
#3 preg_split() most closely aligns with the plain-English intent of your task AND it provides the exact output as its return value.
var_export(preg_split('~(?:(?:^|})[^{]*{)|}[^{]*$~', $url, 0, PREG_SPLIT_NO_EMPTY));
My pattern, while admittedly unsavoury to the novice regex pattern designer AND slightly less efficient because it is making "branched" matches (|), basically says: "Split the string at the following delimiters:
from the start of the string or from a }, including all non-{ characters, then the first encountered { (this is the end of the delimiter).
from the lasts }, including all non-{ characters until the end of the string."
really struggling with this...hopefully someone can put me on the right path to a solution.
My input string is structured like this:
66-2141-A-AC107-7
I'm interested in extracting the string 'AC107' using a single regular expression. I know how to do this with other PHP string functions, but I have to do this with a regular expression.
What I need is to extract all data between the third and fourth hyphens. The structure of each section is not fixed (i.e, 66 may be 8798709 and 2141 may be 38). The presence of the number of hyphens is guaranteed (i.e., there will always be a total of four (4) hyphens).
Any help/guidance is greatly appreciated!
This will do what you need:
(?:[^-]*-){3}([^-]+)
Debuggex Demo
Explanation:
(?:[^-]*-) Look for zero or more non-hyphen characters followed by a hyphen
{3} Look for three of the blocks just described
([^-]+) Capture all the consecutive non-hyphen characters from that point forward (will automatically cut off before the next hyphen)
You can use it in PHP like this:
$str = '66-2141-A-AC107-7';
preg_match('/^(?:[^-]*-){3}([^-]+)/', $str, $matches);
echo $matches[1]; // prints AC107
This should look for anything followed by a hyphen 3 times and then in group 2 (the second set of parenthesis) it will have your value, followed by another hyphen and anything else.
/^(.*-){3}(.*)-(.*)/
You can access it by using $2. In php, it would be like this:
$string = '66-2141-A-AC107-7';
preg_match('/^(.*-){3}(.*)-(.*)/', $string, $matches);
$special_id = $matches[2];
print $special_id;