In PHP I have string with nested brackets:
bar[foo[test[abc][def]]bar]foo
I need a regex that matches the inner bracket-pairs first, so the order in which preg_match_all finds the matching bracket-pairs should be:
[abc]
[def]
[test[abc][def]]
[foo[test[abc][def]]bar]
All texts may vary.
Is this even possible with preg_match_all ?
This is not possible with regular expressions. No matter how complex your regex, it will always return the left-most match first.
At best, you'd have to use multiple regexes, but even then you're going to have trouble because regexes can't really count matching brackets. Your best bet is to parse this string some other way.
Is not evident in your question what kind of "structure of matches" you whant... But you can use only simple arrays. Try
preg_match_all('#\[([a-z\)\(]+?)\]#',$original,$m);
that, for $original = 'bar[foo[test[abc][def]]bar]foo' returns an array with "abc" and "def", the inner ones.
For your output, you need a loop for the "parsing task".
PCRE with preg_replace_callback is better for parsing.
Perhaps this loop is a good clue for your problem,
$original = 'bar[foo[test[abc][def]]bar]foo';
for( $aux=$oldAux=$original;
$oldAux!=($aux=printInnerBracket($aux));
$oldAux=$aux
);
print "\n-- $aux";
function printInnerBracket($s) {
return preg_replace_callback(
'#\[([a-z\)\(]+?)\]#', // the only one regular expression
function($m) {
print "\n$m[0]";
return "($m[1])";
},
$s
);
}
Result (the callback print):
[abc]
[def]
[test(abc)(def)]
[foo(test(abc)(def))bar]
-- bar(foo(test(abc)(def))bar)foo
See also this related question.
Related
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 an array full of patterns that I need matched. Any way to do that, other than a for() loop? Im trying to do it in the least CPU intensive way, since I will be doing dozens of these every minute.
Real world example is, Im building a link status checker, which will check links to various online video sites, to ensure that the videos are still live. Each domain has several "dead keywords", if these are found in the html of a page, that means the file was deleted. These are stored in the array. I need to match the contents pf the array, against the html output of the page.
First of all, if you literally are only doing dozens every minute, then I wouldn't worry terribly about the performance in this case. These matches are pretty quick, and I don't think you're going to have a performance problem by iterating through your patterns array and calling preg_match separately like this:
$matches = false;
foreach ($pattern_array as $pattern)
{
if (preg_match($pattern, $page))
{
$matches = true;
}
}
You can indeed combine all the patterns into one using the or operator like some people are suggesting, but don't just slap them together with a |. This will break badly if any of your patterns contain the or operator.
I would recommend at least grouping your patterns using parenthesis like:
foreach ($patterns as $pattern)
{
$grouped_patterns[] = "(" . $pattern . ")";
}
$master_pattern = implode($grouped_patterns, "|");
But... I'm not really sure if this ends up being faster. Something has to loop through them, whether it's the preg_match or PHP. If I had to guess I'd guess that individual matches would be close to as fast and easier to read and maintain.
Lastly, if performance is what you're looking for here, I think the most important thing to do is pull out the non regex matches into a simple "string contains" check. I would imagine that some of your checks must be simple string checks like looking to see if "This Site is Closed" is on the page.
So doing this:
foreach ($strings_to_match as $string_to_match)
{
if (strpos($page, $string_to_match) !== false))
{
// etc.
break;
}
}
foreach ($pattern_array as $pattern)
{
if (preg_match($pattern, $page))
{
// etc.
break;
}
}
and avoiding as many preg_match() as possible is probably going to be your best gain. strpos() is a lot faster than preg_match().
// assuming you have something like this
$patterns = array('a','b','\w');
// converts the array into a regex friendly or list
$patterns_flattened = implode('|', $patterns);
if ( preg_match('/'. $patterns_flattened .'/', $string, $matches) )
{
}
// PS: that's off the top of my head, I didn't check it in a code editor
If your patterns don't contain many whitespaces, another option would be to eschew the arrays and use the /x modifier. Now your list of regular expressions would look like this:
$regex = "/
pattern1| # search for occurences of 'pattern1'
pa..ern2| # wildcard search for occurences of 'pa..ern2'
pat[ ]tern| # search for 'pat tern', whitespace is escaped
mypat # Note that the last pattern does NOT have a pipe char
/x";
With the /x modifier, whitespace is completely ignored, except when in a character class or preceded by a backslash. Comments like above are also allowed.
This would avoid the looping through the array.
If you're merely searching for the presence of a string in another string, use strpos as it is faster.
Otherwise, you could just iterate over the array of patterns, calling preg_match each time.
If you have a bunch of patterns, what you can do is concatenate them in a single regular expression and match that. No need for a loop.
What about doing a str_replace() on the HTML you get using your array and then checking if the original HTML is equal to the original? This would be very fast:
$sites = array(
'you_tube' => array('dead', 'moved'),
...
);
foreach ($sites as $site => $deadArray) {
// get $html
if ($html == str_replace($deadArray, '', $html)) {
// video is live
}
}
You can combine all the patterns from the list to single regular expression using implode() php function. Then test your string at once using preg_match() php function.
$patterns = array(
'abc',
'\d+h',
'[abc]{6,8}\-\s*[xyz]{6,8}',
);
$master_pattern = '/(' . implode($patterns, ')|(') . ')/'
if(preg_match($master_pattern, $string_to_check))
{
//do something
}
Of course there could be even less code using implode() inline in "if()" condition instead of $master_pattern variable.
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.
I need to read a string, detect a {VAR}, and then do a file_get_contents('VAR.php') in place of {VAR}. The "VAR" can be named anything, like TEST, or CONTACT-FORM, etc. I don't want to know what VAR is -- not to do a hard-coded condition, but to just see an uppercase alphanumeric tag surrounded by curly braces and just do a file_get_contents() to load it.
I know I need to use preg_match and preg_replace, but I'm stumbling through the RegExps on this.
How is this useful? It's useful in hooking WordPress.
Orion above has a right solution, but it's not really necessary to use a callback function in your simple case.
Assuming that the filenames are A-Z + hyphens you can do it in 1 line using PHP's /e flag in the regex:
$str = preg_replace('/{([-A-Z]+)}/e', 'file_get_contents(\'$1.html\')', $str);
This'll replace any instance of {VAR} with the contents of VAR.html. You could prefix a path into the second term if you need to specify a particular directory.
There are the same vague security worries as outlined above, but I can't think of anything specific.
You'll need to do a number of things. I'm assuming you can do the legwork to get the page data you want to preprocess into a string.
First, you'll need the regular expression to match correctly. That should be fairly easy with something like /{\w+}/.
Next you'll need to use all of the flags to preg_match to get the offset location in the page data. This offset will let you divide the string into the before, matching, and after parts of the match.
Once you have the 3 parts, you'll need to run your include, and stick them back together.
Lather, rinse, repeat.
Stop when you find no more variables.
This isn't terribly efficient, and there are probably better ways. You may wish to consider doing a preg_split instead, splitting on /[{}]/. No matter how you slice it you're assuming that you can trust your incoming data, and this will simplify the whole process a lot. To do this, I'd lay out the code like so:
Take your content and split it like so: $parts = preg_split('/[{}]/', $page_string);
Write a recursive function over the parts with the following criteria:
Halt when length of arg is < 3
Else, return a new array composed of
$arg[0] . load_data($arg[1]) . $arg[2]
plus whatever is left in $argv[3...]
Run your function over $parts.
You can do it without regexes (god forbid), something like:
//return true if $str ends with $sub
function endsWith($str,$sub) {
return ( substr( $str, strlen( $str ) - strlen( $sub ) ) === $sub );
}
$theStringWithVars = "blah.php cool.php awesome.php";
$sub = '.php';
$splitStr = split(" ", $theStringWithVars);
for($i=0;$i<count($splitStr);$i++) {
if(endsWith(trim($splitStr[$i]),$sub)) {
//file_get_contents($splitStr[$i]) etc...
}
}
Off the top of my head, you want this:
// load the "template" file
$input = file_get_contents($template_file_name);
// define a callback. Each time the regex matches something, it will call this function.
// whatever this function returns will be inserted as the replacement
function replaceCallback($matches){
// match zero will be the entire match - eg {FOO}.
// match 1 will be just the bits inside the curly braces because of the grouping parens in the regex - eg FOO
// convert it to lowercase and append ".html", so you're loading foo.html
// then return the contents of that file.
// BEWARE. GIANT MASSIVE SECURITY HOLES ABOUND. DO NOT DO THIS
return file_get_contents( strtolower($matches[1]) . ".html" );
};
// run the actual replace method giving it our pattern, the callback, and the input file contents
$output = preg_replace_callback("\{([-A-Z]+)\}", replaceCallback, $input);
// todo: print the output
Now I'll explain the regex
\{([-A-Z]+)\}
The \{ and \} just tell it to match the curly braces. You need the slashes, as { and } are special characters, so they need escaping.
The ( and ) create a grouping. Basically this lets you extract particular parts of the match. I use it in the function above to just match the things inside the braces, without matching the braces themselves. If I didn't do this, then I'd need to strip the { and } out of the match, which would be annoying
The [-A-Z] says "match any uppercase character, or a -
The + after the [-A-Z] means we need to have at least 1 character, but we can have up to any number.
Comparatively speaking, regular expression are expensive. While you may need them to figure out which files to load, you certainly don't need them for doing the replace, and probably shouldn't use regular expressions. After all, you know exactly what you are replacing so why do you need fuzzy search?
Use an associative array and str_replace to do your replacements. str_replace supports arrays for doing multiple substitutions at once. One line substitution, no loops.
For example:
$substitutions = array('{VAR}'=>file_get_contents('VAR.php'),
'{TEST}'=>file_get_contents('TEST.php'),
...
);
$outputContents = str_replace( array_keys($substitutions), $substitutions, $outputContents);
I have an array full of patterns that I need matched. Any way to do that, other than a for() loop? Im trying to do it in the least CPU intensive way, since I will be doing dozens of these every minute.
Real world example is, Im building a link status checker, which will check links to various online video sites, to ensure that the videos are still live. Each domain has several "dead keywords", if these are found in the html of a page, that means the file was deleted. These are stored in the array. I need to match the contents pf the array, against the html output of the page.
First of all, if you literally are only doing dozens every minute, then I wouldn't worry terribly about the performance in this case. These matches are pretty quick, and I don't think you're going to have a performance problem by iterating through your patterns array and calling preg_match separately like this:
$matches = false;
foreach ($pattern_array as $pattern)
{
if (preg_match($pattern, $page))
{
$matches = true;
}
}
You can indeed combine all the patterns into one using the or operator like some people are suggesting, but don't just slap them together with a |. This will break badly if any of your patterns contain the or operator.
I would recommend at least grouping your patterns using parenthesis like:
foreach ($patterns as $pattern)
{
$grouped_patterns[] = "(" . $pattern . ")";
}
$master_pattern = implode($grouped_patterns, "|");
But... I'm not really sure if this ends up being faster. Something has to loop through them, whether it's the preg_match or PHP. If I had to guess I'd guess that individual matches would be close to as fast and easier to read and maintain.
Lastly, if performance is what you're looking for here, I think the most important thing to do is pull out the non regex matches into a simple "string contains" check. I would imagine that some of your checks must be simple string checks like looking to see if "This Site is Closed" is on the page.
So doing this:
foreach ($strings_to_match as $string_to_match)
{
if (strpos($page, $string_to_match) !== false))
{
// etc.
break;
}
}
foreach ($pattern_array as $pattern)
{
if (preg_match($pattern, $page))
{
// etc.
break;
}
}
and avoiding as many preg_match() as possible is probably going to be your best gain. strpos() is a lot faster than preg_match().
// assuming you have something like this
$patterns = array('a','b','\w');
// converts the array into a regex friendly or list
$patterns_flattened = implode('|', $patterns);
if ( preg_match('/'. $patterns_flattened .'/', $string, $matches) )
{
}
// PS: that's off the top of my head, I didn't check it in a code editor
If your patterns don't contain many whitespaces, another option would be to eschew the arrays and use the /x modifier. Now your list of regular expressions would look like this:
$regex = "/
pattern1| # search for occurences of 'pattern1'
pa..ern2| # wildcard search for occurences of 'pa..ern2'
pat[ ]tern| # search for 'pat tern', whitespace is escaped
mypat # Note that the last pattern does NOT have a pipe char
/x";
With the /x modifier, whitespace is completely ignored, except when in a character class or preceded by a backslash. Comments like above are also allowed.
This would avoid the looping through the array.
If you're merely searching for the presence of a string in another string, use strpos as it is faster.
Otherwise, you could just iterate over the array of patterns, calling preg_match each time.
If you have a bunch of patterns, what you can do is concatenate them in a single regular expression and match that. No need for a loop.
What about doing a str_replace() on the HTML you get using your array and then checking if the original HTML is equal to the original? This would be very fast:
$sites = array(
'you_tube' => array('dead', 'moved'),
...
);
foreach ($sites as $site => $deadArray) {
// get $html
if ($html == str_replace($deadArray, '', $html)) {
// video is live
}
}
You can combine all the patterns from the list to single regular expression using implode() php function. Then test your string at once using preg_match() php function.
$patterns = array(
'abc',
'\d+h',
'[abc]{6,8}\-\s*[xyz]{6,8}',
);
$master_pattern = '/(' . implode($patterns, ')|(') . ')/'
if(preg_match($master_pattern, $string_to_check))
{
//do something
}
Of course there could be even less code using implode() inline in "if()" condition instead of $master_pattern variable.