I am currently working at a project involving regex in php. I wanted to know why or how can I get this recursive regular expression to work in PHP:
{{test":"([a-f0-9]{32})"},{"test2":"([a-z]{3})}}
And the given results should be an array with:
[a-f0-9]{32}
[a-z]{3}
Maybe, this regex helps
/.sample.\/.*?(\d+\.\d+\.\d+)-/
You should escape the . or it will mean any character.
If it does not matter, what is after the dash, you need not use the anchor $ for end of string.
This finds the first occurence of number in the string, because .*? is not eager. It matches only as much as necessary for the rest of the pattern.
You can use this, if between / and the number are only letters allowed:
/.sample.\/[a-zA-Z]*(\d+\.\d+\.\d+)-/
I have a string. An example might be "Contact /u/someone on reddit, or visit /r/subreddit or /r/subreddit2"
I want to replace any instance of "/r/x" and "/u/x" with "[/r/x](http://reddit.com/r/x)" and "[/u/x](http://reddit.com/u/x)" basically.
So I'm not sure how to 1) find "/r/" and then expand that to the rest of the word (until there's a space), then 2) take that full "/r/x" and replace with my pattern, and most importantly 3) do this for all "/r/" and "/u/" matches in a single go...
The only way I know to do this would be to write a function to walk the string, character by character, until I found "/", then look for "r" and "/" to follow; then keep going until I found a space. That would give me the beginning and ending characters, so I could do a string replacement; then calculate the new end point, and continue walking the string.
This feels... dumb. I have a feeling there's a relatively simple way to do this, and I just don't know how to google to get all the relevant parts.
A simple preg_replace will do what you want.
Try:
$string = preg_replace('#(/(?:u|r)/[a-zA-Z0-9_-]+)#', '[\1](http://reddit.com\1)', $string);
Here is an example: http://ideone.com/dvz2zB
You should see if you can discover what characters are valid in a Reddit name or in a Reddit username and modify the [a-zA-Z0-9_-] charset accordingly.
You are looking for a regular expression.
A basic pattern starts out as a fixed string. /u/ or /r/ which would match those exactly. This can be simplified to match one or another with /(?:u|r)/ which would match the same as those two patterns. Next you would want to match everything from that point up to a space. You would use a negative character group [^ ] which will match any character that is not a space, and apply a modifier, *, to match as many characters as possible that match that group. /(?:u|r)/[^ ]*
You can take that pattern further and add a lookbehind, (?<= ) to ensure your match is preceded by a space so you're not matching a partial which results in (?<= )/(?:u|r)/[^ ]*. You wrap all of that to make a capturing group ((?<= )/(?:u|r)/[^ ]*). This will capture the contents within the parenthesis to allow for a replacement pattern. You can express your chosen replacement using the \1 reference to the first captured group as [\1](http://reddit.com\1).
In php you would pass the matching pattern, replacement pattern, and subject string to the preg_replace function.
In my opinion regex would be an overkill for such a simple operation. If you just want to replace instance of "/r/x" with "[r/x](http://reddit.com/r/x)" and "/u/x" with "[/u/x](http://reddit.com/u/x)" you should use str_replace although with preg_replace it'll lessen the code.
str_replace("/r/x","[/r/x](http://reddit.com/r/x)","whatever_string");
use regex for intricate search string and replace. you can also use http://www.jslab.dk/tools.regex.php regular expression generator if you have something complex to capture in the string.
I am facing difficulties to validate the below format. I want regular expression needs to be satisfied with the below condition.
$pattern = '/^\w[\w\s\.\%\-\(\)\[\]]*$/u';
$file_name = "(00)filename.jpg";
if(preg_match($pattern,$file_name)){
echo "Pattern matched";
}else {
echo "Pattern not matched";
}
I have tried several ways. But, the main problem is do not write the own pregmatch, instead need to modify the existing one which accepts the brackets().
So this should match (00)filename.jpg and does not, because your regex requires the string to ^\w start with a word-character. You can add optional parenthesized \w+ to the start:
^(?:\(\w+\)|\w)[-\w\s.%()[\]]*$
Also need to put the hyphen - at the start or end inside the character class. Else it would express a range. Furthermore need to escape the closing ] inside the character class.
test at regex101
But possibly, you just want to check:
if there's at least one word-character in the string.
the string consist only of [-\w\s.%()[\]]
If so, use a lookahead to check for the \w:
^(?=.*?\w)[-\w\s.%()[\]]+$
test at regex101
I'm currently building a chat system with reply function.
How can I match the numbers inside the '#' symbol and brackets, example: #[123456789]
This one works in JavaScript
/#\[(0-9_)+\]/g
But it doesn't work in PHP as it cannot recognize the /g modifier. So I tried this:
/\#\[[^0-9]\]/
I have the following example code:
$example_message = 'Hi #[123456789] :)';
$msg = preg_replace('/\#\[[^0-9]\]/', '$1', $example_message);
But it doesn't work, it won't capture those numbers inside #[ ]. Any suggestions? Thanks
You have some core problems in your regex, the main one being the ^ that negates your character class. So instead of [^0-9] matching any digit, it matches anything but a digit. Also, the g modifier doesn't exist in PHP (preg_replace() replaces globally and you can use preg_match_all() to match expressions globally).
You'll want to use a regex like /#\[(\d+)\]/ to match (with a group) all of the digits between #[ and ].
To do this globally on a string in PHP, use preg_match_all():
preg_match_all('/#\[(\d+)\]/', 'Hi #[123456789] :)', $matches);
var_dump($matches);
However, your code would be cleaner if you didn't rely on a match group (\d+). Instead you can use "lookarounds" like: (?<=#\[)\d+(?=\]). Also, if you will only have one digit per string, you should use preg_match() not preg_match_all().
Note: I left the example vague and linked to lots of documentation so you can read/learn better. If you have any questions, please ask. Also, if you want a better explanation on the regular expressions used (specifically the second one with lookarounds), let me know and I'll gladly elaborate.
Use the preg_match_all function in PHP if you’d like to produce the behaviour of the g modifier in Javascript. Use the preg_match function otherwise.
preg_match_all("/#\\[([0-9]+)\\]/", $example_message, $matches);
Explanation:
/ opening delimiter
# match the at sign
\\[ match the opening square bracket (metacharacter, so needs to be escaped)
( start capturing
[0-9] match a digit
+ match the previous once or more
) stop capturing
\\] match the closing square bracket (metacharacter, so needs to be escaped)
/ closing delimiter
Now $matches[1] contains all the numbers inside the square brackets.
I am trying to search for some pattern in PHP with the help of preg_match. Search pattern is like this (but this is wrong):
/[\d\s*-\s*\d\s*(usd|eur)]{1}/i
\d starts with integer,
\s* there can be any number of whitespaces,
- there must be exactly one minus sign
\s* there can be any number of whitespaces,
\d then must be integer
\s* there can be any number of whitespaces,
(usd|eur) any of the following words must be present but one
[\d\s*-\s*\d\s*(usd|eur)]{1} - in string there should be exactly one occurence
the above pattern does not work, what I am doing wrong? For testing:
<?php
$pattern = '/[\d\s*-\s*\d\s*(usd|eur)]{1}/i';
$query = '100-120 100-120';
echo $pattern.'<br/>';
echo $query.'<br/>';
if(preg_match($pattern, $query))
echo 'OK';
else
echo 'not OK!';
?>
Note:
I am trying to pull out data like this:
The price of item is 100 - 120 usd in our market
[...] is a character class. It means "match any one of these characters". [abc] will match a,b, or c. It doesn't match the string "abc".
In addition:
{1} means "match the preceding expression one time". However, matching once is the default. There is no need to explicitly tell it to match one time.
\d matches a single numeric digit. Based on your example, you want \d+ - match a number made up of at least one digit.
Here is what your pattern should look like:
/\d+\s*-\s*\d+\s*(usd|eur)/i
Regular expressions are a powerful tool for examining and modifying text. Regular expressions themselves, with a general pattern notation almost like a mini programming language, allow you to describe and parse text. They enable you to search for patterns within a string, extracting matches flexibly and precisely. However, you should note that because regular expressions are more powerful, they are also slower than the more basic string functions. You should only use regular expressions if you have a particular need.
This tutorial gives a brief overview of basic regular expression syntax and then considers the functions that PHP provides for working with regular expressions.
The Basics
Matching Patterns
Replacing Patterns
Array Processing
PHP supports two different types of regular expressions: POSIX-extended and Perl-Compatible Regular Expressions (PCRE). The PCRE functions are more powerful than the POSIX ones, and faster too, so we will concentrate on them.
The Basics
In a regular expression, most characters match only themselves. For instance, if you search for the regular expression "foo" in the string "John plays football," you get a match because "foo" occurs in that string. Some characters have special meanings in regular expressions. For instance, a dollar sign ($) is used to match strings that end with the given pattern. Similarly, a caret (^) character at the beginning of a regular expression indicates that it must match the beginning of the string. The characters that match themselves are called literals. The characters that have special meanings are called metacharacters.
The dot (.) metacharacter matches any single character except newline (). So, the pattern h.t matches hat, hothit, hut, h7t, etc. The vertical pipe (|) metacharacter is used for alternatives in a regular expression. It behaves much like a logical OR operator and you should use it if you want to construct a pattern that matches more than one set of characters. For instance, the pattern Utah|Idaho|Nevada matches strings that contain "Utah" or "Idaho" or "Nevada". Parentheses give us a way to group sequences. For example, (Nant|b)ucket matches "Nantucket" or "bucket". Using parentheses to group together characters for alternation is called grouping.
If you want to match a literal metacharacter in a pattern, you have to escape it with a backslash.
To specify a set of acceptable characters in your pattern, you can either build a character class yourself or use a predefined one. A character class lets you represent a bunch of characters as a single item in a regular expression. You can build your own character class by enclosing the acceptable characters in square brackets. A character class matches any one of the characters in the class. For example a character class [abc] matches a, b or c. To define a range of characters, just put the first and last characters in, separated by hyphen. For example, to match all alphanumeric characters: [a-zA-Z0-9]. You can also create a negated character class, which matches any character that is not in the class. To create a negated character class, begin the character class with ^: [^0-9].
The metacharacters +, *, ?, and {} affect the number of times a pattern should be matched. + means "Match one or more of the preceding expression", * means "Match zero or more of the preceding expression", and ? means "Match zero or one of the preceding expression". Curly braces {} can be used differently. With a single integer, {n} means "match exactly n occurrences of the preceding expression", with one integer and a comma, {n,} means "match n or more occurrences of the preceding expression", and with two comma-separated integers {n,m} means "match the previous character if it occurs at least n times, but no more than m times".
Now, have a look at the examples:
Regular Expression Will match...
foo The string "foo"
^foo "foo" at the start of a string
foo$ "foo" at the end of a string
^foo$ "foo" when it is alone on a string
[abc] a, b, or c
[a-z] Any lowercase letter
[^A-Z] Any character that is not a uppercase letter
(gif|jpg) Matches either "gif" or "jpeg"
[a-z]+ One or more lowercase letters
[0-9\.\-] Аny number, dot, or minus sign
^[a-zA-Z0-9_]{1,}$ Any word of at least one letter, number or _
([wx])([yz]) wy, wz, xy, or xz
[^A-Za-z0-9] Any symbol (not a number or a letter)
([A-Z]{3}|[0-9]{4}) Matches three letters or four numbers
Perl-Compatible Regular Expressions emulate the Perl syntax for patterns, which means that each pattern must be enclosed in a pair of delimiters. Usually, the slash (/) character is used. For instance, /pattern/.
The PCRE functions can be divided in several classes: matching, replacing, splitting and filtering.
Matching Patterns
The preg_match() function performs Perl-style pattern matching on a string. preg_match() takes two basic and three optional parameters. These parameters are, in order, a regular expression string, a source string, an array variable which stores matches, a flag argument and an offset parameter that can be used to specify the alternate place from which to start the search:
preg_match ( pattern, subject [, matches [, flags [, offset]]])
The preg_match() function returns 1 if a match is found and 0 otherwise. Let's search the string "Hello World!" for the letters "ll":
<?php
if (preg_match("/ell/", "Hello World!", $matches)) {
echo "Match was found <br />";
echo $matches[0];
}
?>
The letters "ll" exist in "Hello", so preg_match() returns 1 and the first element of the $matches variable is filled with the string that matched the pattern. The regular expression in the next example is looking for the letters "ell", but looking for them with following characters:
<?php
if (preg_match("/ll.*/", "The History of Halloween", $matches)) {
echo "Match was found <br />";
echo $matches[0];
}
?>
Now let's consider more complicated example. The most popular use of regular expressions is validation. The example below checks if the password is "strong", i.e. the password must be at least 8 characters and must contain at least one lower case letter, one upper case letter and one digit:
<?php
$password = "Fyfjk34sdfjfsjq7";
if (preg_match("/^.*(?=.{8,})(?=.*\d)(?=.*[a-z])(?=.*[A-Z]).*$/", $password)) {
echo "Your passwords is strong.";
} else {
echo "Your password is weak.";
}
?>
The ^ and $ are looking for something at the start and the end of the string. The ".*" combination is used at both the start and the end. As mentioned above, the .(dot) metacharacter means any alphanumeric character, and * metacharacter means "zero or more". Between are groupings in parentheses. The "?=" combination means "the next text must be like this". This construct doesn't capture the text. In this example, instead of specifying the order that things should appear, it's saying that it must appear but we're not worried about the order.
The first grouping is (?=.{8,}). This checks if there are at least 8 characters in the string. The next grouping (?=.[0-9]) means "any alphanumeric character can happen zero or more times, then any digit can happen". So this checks if there is at least one number in the string. But since the string isn't captured, that one digit can appear anywhere in the string. The next groupings (?=.[a-z]) and (?=.[A-Z]) are looking for the lower case and upper case letter accordingly anywhere in the string.
Finally, we will consider regular expression that validates an email address:
<?php
$email = firstname.lastname#aaa.bbb.com;
$regexp = "/^[^0-9][A-z0-9_]+([.][A-z0-9_]+)*[#][A-z0-9_]+([.][A-z0-9_]+)*[.][A-z]{2,4}$/";
if (preg_match($regexp, $email)) {
echo "Email address is valid.";
} else {
echo "Email address is <u>not</u> valid.";
}
?>
This regular expression checks for the number at the beginning and also checks for multiple periods in the user name and domain name in the email address. Let's try to investigate this regular expression yourself.
For the speed reasons, the preg_match() function matches only the first pattern it finds in a string. This means it is very quick to check whether a pattern exists in a string. An alternative function, preg_match_all(), matches a pattern against a string as many times as the pattern allows, and returns the number of times it matched.
Replacing Patterns
In the above examples, we have searched for patterns in a string, leaving the search string untouched. The preg_replace() function looks for substrings that match a pattern and then replaces them with new text. preg_replace() takes three basic parameters and an additional one. These parameters are, in order, a regular expression, the text with which to replace a found pattern, the string to modify, and the last optional argument which specifies how many matches will be replaced.
preg_replace( pattern, replacement, subject [, limit ])
The function returns the changed string if a match was found or an unchanged copy of the original string otherwise. In the following example we search for the copyright phrase and replace the year with the current.
<?php
echo preg_replace("/([Cc]opyright) 200(3|4|5|6)/", "$1 2007", "Copyright 2005");
?>
In the above example we use back references in the replacement string. Back references make it possible for you to use part of a matched pattern in the replacement string. To use this feature, you should use parentheses to wrap any elements of your regular expression that you might want to use. You can refer to the text matched by subpattern with a dollar sign ($) and the number of the subpattern. For instance, if you are using subpatterns, $0 is set to the whole match, then $1, $2, and so on are set to the individual matches for each subpattern.
In the following example we will change the date format from "yyyy-mm-dd" to "mm/dd/yyy":
<?php
echo preg_replace("/(\d+)-(\d+)-(\d+)/", "$2/$3/$1", "2007-01-25");
?>
We also can pass an array of strings as subject to make the substitution on all of them. To perform multiple substitutions on the same string or array of strings with one call to preg_replace(), we should pass arrays of patterns and replacements. Have a look at the example:
<?php
$search = array ( "/(\w{6}\s\(w{2})\s(\w+)/e",
"/(\d{4})-(\d{2})-(\d{2})\s(\d{2}:\d{2}:\d{2})/");
$replace = array ('"$1 ".strtoupper("$2")',
"$3/$2/$1 $4");
$string = "Posted by John | 2007-02-15 02:43:41";
echo preg_replace($search, $replace, $string);?>
In the above example we use the other interesting functionality - you can say to PHP that the match text should be executed as PHP code once the replacement has taken place. Since we have appended an "e" to the end of the regular expression, PHP will execute the replacement it makes. That is, it will take strtoupper(name) and replace it with the result of the strtoupper() function, which is NAME.
Array Processing
PHP's preg_split() function enables you to break a string apart basing on something more complicated than a literal sequence of characters. When it's necessary to split a string with a dynamic expression rather than a fixed one, this function comes to the rescue. The basic idea is the same as preg_match_all() except that, instead of returning matched pieces of the subject string, it returns an array of pieces that didn't match the specified pattern. The following example uses a regular expression to split the string by any number of commas or space characters:
<?php
$keywords = preg_split("/[\s,]+/", "php, regular expressions");
print_r( $keywords );
?>
Another useful PHP function is the preg_grep() function which returns those elements of an array that match a given pattern. This function traverses the input array, testing all elements against the supplied pattern. If a match is found, the matching element is returned as part of the array containing all matches. The following example searches through an array and all the names starting with letters A-J:
<?php
$names = array('Andrew','John','Peter','Nastin','Bill');
$output = preg_grep('/^[a-m]/i', $names);
print_r( $output );
?>