I have a string like this:
$string = '[Canada] [United States]';
I need to detect something like this
if($string contains Canada) {
// Do stuff for Canada
}
You could pull out all text between [ and ] and then see if it is found in the resulting array.
preg_match_all('/\[(.*?)\]/', $string, $matches);
if (in_array('Canada', $matches[1])) {
echo 'Hello, Canada!';
}
CodePad.
If you just used substring searching functions, you'd run the risk that the string you searched for was the substring of a larger block between brackets.
If you are doing simple text matching, and don't want the overhead of using the regular expressions engines, the strpos function may be what you are looking for.
See the PHP Manual page for strpos for more details.
if(strpos($string,"Canada")!==FALSE){
// Do stuff for Canada
}
The use of the strpos() function is preferred over strstr() due to the manual stating that for instances that the programmer only cares about finding a match, not where the match is located, strpos() is faster and less memory intensive.
Use strstr().
Related
I am trying to handle parameters like Java or PHP natively handle them, using Regex to parse variable numbers (and types) of arguments. For example, a function might be:
util.echo(5, "Hello, world!");
In this instance, I would want to separate 5 as the first argument and "Hello, world!" as the second (without quotes). What I currently do is explode by commas, but that runs into issues if the string parameters include a comma. I don't have much experience with Regex, but I think it has some way of ignoring commas that are within quotes.
The Regex from this question (",(?=(?:[^\"]*\"[^\"]*\")*[^\"]*$)") seems like it could work, but I'm confused on how to implement it with PHP.
To test a regular expression onto a string, you can use the preg_match() function in PHP.
See the manual
// $matches is going to output the matches
preg_match("/,(?=(?:[^\"]*\"[^\"]*\")*[^\"]*$)/", $to_be_checked, $matches);
if($matches){
var_dump($matches);
// there was a match!
} else {
// the regular expression did not find any pattern matches
}
if you don't need to access the exact matches, just if there was at least one pattern match, you can simply do this:
if(preg_match("/,(?=(?:[^\"]*\"[^\"]*\")*[^\"]*$)/", $to_be_checked)){
// there was a match!
} else {
// the regular expression did not find any pattern matches
}
Thank you to Zac and The fourth bird! Example solution that works, for future reference:
$parameters = 'util.echo(5, "Hello, world!");';
preg_match_all('/(?:[^\s(]+\(|\G(?!^),\s*)\K(?:"[^"]*"|[^,()]+)(?=[^()]*\);)/', $parameters, $matches);
if($matches){
var_dump($matches[0]);
} else {
echo('No matches.');
}
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."
I have a list of words in an array. What is the fastest way to check if any of these words exist in an string?
Currently, I am checking the existence of array elements one by one through a foreach loop by stripos. I am curious if there is a faster method, like what we do for str_replace using an array.
Regarding to your additional comment you could explode your string into single words using explode() or preg_split() and then check this array against the needles-array using array_intersect(). So all the work is done only once.
<?php
$haystack = "Hello Houston, we have a problem";
$haystacks = preg_split("/\b/", $haystack);
$needles = array("Chicago", "New York", "Houston");
$intersect = array_intersect($haystacks, $needles);
$count = count($intersect);
var_dump($count, $intersect);
I could imagine that array_intersect() is pretty fast. But it depends what you really want (matching words, matching fragments, ..)
my personal function:
function wordsFound($haystack,$needles) {
return preg_match('/\b('.implode('|',$needles).')\b/i',$haystack);
}
//> Usage:
if (wordsFound('string string string',array('words')))
Notice if you work with UTF-8 exotic strings you need to change \b with teh corrispondent of utf-8 preg word boundary
Notice2: be sure to enter only a-z0-9 chars in $needles (thanks to MonkeyMonkey) otherwise you need to preg_quote it before
Notice3: this function is case insensitve thanks to i modifier
In general regular expressions are slower compared to basic string functions like str_ipos(). But I think it really depends on the situation. If you really need the maximum performance, I suggest making some tests with real-world data.
What is the best way to search for a word in a string
preg_match("/word/",$string)
stripos("word",$string)
Or is there a better way
One benefit to using regexp for this job is the ability to use \b (Regexp word boundary) in the regexp, and other random derivations. If you are only looking for that sequence of letters in a string stripos is likely to be a little better.
$tests = array("word", "worded", "This also has the word.", "Words are not the same", "Word capitalized should match");
foreach ($tests as $string)
{
echo "Testing \"$string\": Regexp:";
echo preg_match("/\bword\b/i", $string) ? "Matched" : "Failed";
echo " stripos:";
echo stripos("word", $string) >= 0 ? "Matched": "Failed";
echo "\n";
}
Results:
Testing "word": Regexp:Matched stripos:Matched
Testing "worded": Regexp:Failed stripos:Matched
Testing "This also has the word.": Regexp:Matched stripos:Matched
Testing "Words are not the same": Regexp:Failed stripos:Matched
Testing "Word capitalized should match": Regexp:Matched stripos:Matched
Like it says in the Notes for preg_match:
Do not use preg_match() if you only want to check if one string is contained in another string. Use strpos() or strstr() instead as they will be faster.
If you are simply looking for a substring, stripos() or strpos() and friends are much better than using the preg family of functions.
For simple string matching the PHP string functions offer more performance. Regex is more heavyweight and therefore has lower performance.
Having said that, in most cases, the performance difference is small enough to go unnoticed, unless you're looping over an array with hundreds of thousands of elements or more.
Of course, as soon as you start needing "cleverer" matching, regex becomes the only game in town.
There is also substr_count($haystack, $needle) which just returns the number of substring occurences. With the added bonus of not having to worry about 0 equating to false like stripos() if the first occurrence is at position 0. Although that's not a problem if you use strict equality.
http://php.net/manual/en/function.substr-count.php
It's been several years since I have used regular expressions, and I was hoping I could get some help on something I'm working on. You know how google's search is quite powerful and will take stuff inside quotes as a literal phrase and things with a minus sign in front of them as not included.
Example: "this is literal" -donotfindme site:examplesite.com
This example would search for the phrase "this is literal" in sites that don't include the word donotfindme on the webiste examplesite.com.
Obviously I'm not looking for something as complex as Google I just wanted to reference where my project is heading.
Anyway, I first wanted to start with the basics which is the literal phrases inside quotes. With the help of another question on this site I was able to do the following:
(this is php)
$search = 'hello "this" is regular expressions';
$pattern = '/".*"/';
$regex = preg_match($pattern, $search, $matches);
print_r($matches);
But this outputs "this" instead of the desired this, and doesn't work at all for multiple phrases in quotes. Could someone lead me in the right direction?
I don't necessarily need code even a real nice place with tutorials would probably do the job.
Thanks!
Well, for this example at least, if you want to match only the text inside the quotes you'll need to use a capturing group. Write it like this:
$pattern = '/"(.*)"/';
and then $matches will be an array of length 2 that contains the text between the quotes in element 1. (It'll still contain the full text matched in element 0) In general, you can have more than one set of these parentheses; they're numbered from the left starting at 1, and there will be a corresponding element in $matches for the text that each group matched. Example:
$pattern = '/"([a-z]+) ([a-z]+) (.*)"/';
will select all quoted strings which have two lowercase words separated by a single space, followed by anything. Then $matches[1] will be the first word, $matches[2] the second word, and $matches[3] the "anything".
For finding multiple phrases, you'll need to pick out one at a time with preg_match(). There's an optional "offset" parameter you can pass, which indicates where in the string it should start searching, and to find multiple matches you should give the position right after the previous match as the offset. See the documentation for details.
You could also try searching Google for "regular expression tutorial" or something like that, there are plenty of good ones out there.
Sorry, but my php is a bit rusty, but this code will probably do what you request:
$search = 'hello "this" is regular expressions';
$pattern = '/"(.*)"/';
$regex = preg_match($pattern, $search, $matches);
print_r($matches[1]);
$matches1 will contain the 1st captured subexpression; $matches or $matches[0] contains the full matched patterns.
See preg_match in the PHP documentation for specifics about subexpressions.
I'm not quite sure what you mean by "multiple phrases in quotes", but if you're trying to match balanced quotes, it's a bit more involved and tricky to understand. I'd pick up a reference manual. I highly recommend Mastering Regular Expressions, by Jeffrey E. F. Friedl. It is, by far, the best aid to understanding and using regular expressions. It's also an excellent reference.
Here is the complete answer for all the sort of search terms (literal, minus, quotes,..) WITH replacements . (For google visitors at the least).
But maybe it should not be done with only regular expressions though.
Not only will it be hard for yourself or other developers to work and add functionality on what would be a huge and super complex regular expression otherwise
it might even be that it is faster with this approach.
It might still need a lot of improvement but at least here is a working complete solution in a class. There is a bit more in here than asked in the question, but it illustrates some reasons behind some choices.
class mySearchToSql extends mysqli {
protected function filter($what) {
if (isset(what) {
//echo '<pre>Search string: '.var_export($what,1).'</pre>';//debug
//Split into different desires
preg_match_all('/([^"\-\s]+)|(?:"([^"]+)")|-(\S+)/i',$what,$split);
//echo '<pre>'.var_export($split,1).'</pre>';//debug
//Surround with SQL
array_walk($split[1],'self::sur',array('`Field` LIKE "%','%"'));
array_walk($split[2],'self::sur',array('`Desc` REGEXP "[[:<:]]','[[:>:]]"'));
array_walk($split[3],'self::sur',array('`Desc` NOT LIKE "%','%"'));
//echo '<pre>'.var_export($split,1).'</pre>';//debug
//Add AND or OR
$this ->where($split[3])
->where(array_merge($split[1],$split[2]), true);
}
}
protected function sur(&$v,$k,$sur) {
if (!empty($v))
$v=$sur[0].$this->real_escape_string($v).$sur[1];
}
function where($s,$OR=false) {
if (empty($s)) return $this;
if (is_array($s)) {
$s=(array_filter($s));
if (empty($s)) return $this;
if($OR==true)
$this->W[]='('.implode(' OR ',$s).')';
else
$this->W[]='('.implode(' AND ',$s).')';
} else
$this->W[]=$s;
return $this;
}
function showSQL() {
echo $this->W? 'WHERE '. implode(L.' AND ',$this->W).L:'';
}
Thanks for all stackoverflow answers to get here!
You're in luck because I asked a similar question regarding string literals recently. You can find it here: Regex for managing escaped characters for items like string literals
I ended up using the following for searching for them and it worked perfectly:
(?<!\\)(?:\\\\)*(\"|')((?:\\.|(?!\1)[^\\])*)\1
This regex differs from the others as it properly handles escaped quotation marks inside the string.