How can I replace a string starting with 'a' and ending with 'z'?
basically I want to be able to do the same thing as str_replace but be indifferent to the values in between two strings in a 'haystack'.
Is there a built in function for this? If not, how would i go about efficiently making a function that accomplishes it?
That can be done with Regular Expression (RegEx for short).
Here is a simple example:
$string = 'coolAfrackZInLife';
$replacement = 'Stuff';
$result = preg_replace('/A.*Z/', $replacement, $string);
echo $result;
The above example will return coolStuffInLife
A little explanation on the givven RegEx /A.*Z/:
- The slashes indicate the beginning and end of the Regex;
- A and Z are the start and end characters between which you need to replace;
- . matches any single charecter
- * Zero or more of the given character (in our case - all of them)
- You can optionally want to use + instead of * which will match only if there is something in between
Take a look at Rubular.com for a simple way to test your RegExs. It also provides short RegEx reference
$string = "I really want to replace aFGHJKz with booo";
$new_string = preg_replace('/a[a-zA-z]+z/', 'boo', $string);
echo $new_string;
Be wary of the regex, are you wanting to find the first z or last z? Is it only letters that can be between? Alphanumeric? There are various scenarios you'd need to explain before I could expand on the regex.
use preg_replace so you can use regex patterns.
Related
I'm trying to retrieve the followed by count on my instagram page. I can't seem to get the Regex right and would very much appreciate some help.
Here's what I'm looking for:
y":{"count":
That's the beginning of the string, and I want the 4 numbers after that.
$string = preg_replace("{y"\"count":([0-9]+)\}","",$code);
Someone suggested this ^ but I can't get the formatting right...
You haven't posted your strings so it is a guess to what the regex should be... so I'll answer on why your codes fail.
preg_replace('"followed_by":{"count":\d')
This is very far from the correct preg_replace usage. You need to give it the replacement string and the string to search on. See http://php.net/manual/en/function.preg-replace.php
Your second usage:
$string = preg_replace(/^y":{"count[0-9]/","",$code);
Is closer but preg_replace is global so this is searching your whole file (or it would if not for the anchor) and will replace the found value with nothing. What your really want (I think) is to use preg_match.
$string = preg_match('/y":\{"count(\d{4})/"', $code, $match);
$counted = $match[1];
This presumes your regex was kind of correct already.
Per your update:
Demo: https://regex101.com/r/aR2iU2/1
$code = 'y":{"count:1234';
$string = preg_match('/y":\{"count:(\d{4})/', $code, $match);
$counted = $match[1];
echo $counted;
PHP Demo: https://eval.in/489436
I removed the ^ which requires the regex starts at the start of your string, escaped the { and made the\d be 4 characters long. The () is a capture group and stores whatever is found inside of it, in this case the 4 numbers.
Also if this isn't just for learning you should be prepared for this to stop working at some point as the service provider may change the format. The API is a safer route to go.
This regexp should capture value you're looking for in the first group:
\{"count":([0-9]+)\}
Use it with preg_match_all function to easily capture what you want into array (you're using preg_replace which isn't for retrieving data but for... well replacing it).
Your regexp isn't working because you didn't escaped curly brackets. And also you didn't put count quantifier (plus sign in my example) so it would only capture first digit anyway.
I have many strings that all start with #and a pseudo and I want to change these pseudo via regex to the real name.
I haven't many pseudo (maybe 5 to 10) so I can go with a simple regex like:
$find = array('#alex', '#donald');
$replace = array('Alex A.', 'Donald B.' );
$result= preg_replace($find, $replace, $feed->itemTitle);
My problem is that I already have a pre_replace on these string, that removes the link. So far this is my regex:
<?php echo preg_replace('#(https?://([-\w\.]+[-\w])+(:\d+)?(/([\w/_\.#-]*(\?\S+)?[^\.\s])?)?).....#',' ',$feed->itemTitle); ?>
I can't come up with a solution that will mix the two regex. (regex is something I am not confortable with).
To have already a preg_replace for the links isn't a problem, don't bother about that.
If you want you can build a giant pattern with capture groups to be used with preg_replace_callback that allows the callback function to choose which is the replacement string to return according to the capture group number. However, this isn't the good way.
Since, you want to replace fixed strings (#alex, #donald are fixed strings) the best and fastest way is to use strtr (even if you parse the string a second time):
$trans = array('#alex' => 'Alex A.',
'#donald' => 'Donald B.');
$result = strtr($feed->itemTitle, $trans);
Okay, I was hoping someone could help me with a little regex-fu.
I am trying to clean up a string.
Basically, I am:
Replacing all characters except A-Za-z0-9 with a replacement.
Replacing consecutive duplicates of the replacement with a single instance of the replacement.
Trimming the replacement from the beginning and end of the string.
Example Input:
(&&(%()$()#&#&%&%%(%$+-_The dog jumped over the log*(&)$%&)#)##%&)&^)##)
Required Output:
The+dog+jumped+over+the+log
I am currently using this very discombobulated code and just know there is a much more elegant way to accomplish this....
function clean($string, $replace){
$ok = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
$ok .= $replace;
$pattern = "/[^".preg_quote($ok, "/")."]/";
return trim(preg_replace('/'.preg_quote($replace.$replace).'+/', $replace, preg_replace($pattern, $replace, $string)),$replace);
}
Could a Regex-Fu Master please grace me with a simpler/more efficient solution?
A much better solution suggested and explained by Botond Balázs and hakre:
function clean($string, $replace, $skip=""){
// Escape $skip
$escaped = preg_quote($replace.$skip, "/");
// Regex pattern
// Replace all consecutive occurrences of "Not OK"
// characters with the replacement
$pattern = '/[^A-Za-z0-9'.$escaped.']+/';
// Execute the regex
$result = preg_replace($pattern, $replace, $string);
// Trim and return the result
return trim($result, $replace);
}
I'm not a "regex ninja" but here's how I would do it.
function clean($string, $replace){
/// Remove all "not OK" characters from the beginning and the end:
$result = preg_replace('/^[^A-Za-z0-9]+/', '', $string);
$result = preg_replace('/[^A-Za-z0-9]+$/', '', $result);
// Replace all consecutive occurrences of "not OK"
// characters with the replacement:
$result = preg_replace('/[^A-Za-z0-9]+/', $replace, $result);
return $result;
}
I guess this could be simplified more but when dealing with regexes, clarity and readability is often more important than being clever or writing super-optimal code.
Let's see how it works:
/^[^A-Za-z0-9]+/:
^ matches the beginning of the string.
[^A-Za-z0-9] matches all non-alphanumeric characters
+ means "match one or more of the previous thing"
/[^A-Za-z0-9]+$/:
same thing as above, except $ matches the end of the string
/[^A-Za-z0-9]+/:
same thing as above, except it matches mid-string too
EDIT: OP is right that the first two can be replaced with a call to trim():
function clean($string, $replace){
// Replace all consecutive occurrences of "not OK"
// characters with the replacement:
$result = preg_replace('/[^A-Za-z0-9]+/', $replace, $result);
return trim($result, $replace);
}
I don't want to sound super-clever, but I would not call it regex-foo.
What you do is actually pretty much in the right direction because you use preg_quote, many others are not even aware of that function.
However probably at the wrong place. Wrong place because you quote for characters inside a character class and that has (similar but) different rules for quoting in a regex.
Additionally, regular expressions have been designed with a case like yours in mind. That is probably the part where you look for a wizard, let's see some options how to make your negative character class more compact (I keep the generation out to make this more visible):
[^0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz]
There are constructs like 0-9, A-Z and a-z that can represent exactly that. As you can see - is a special character inside a character class, it is not meant literal but as having some characters from-to:
[^0-9A-Za-z]
So that is already more compact and represents the same. There are also notations like \d and \w which might be handy in your case. But I take the first variant for a moment, because I think it's already pretty visible what it does.
The other part is the repetition. Let's see, there is + which means one or more. So you want to replace one or more of the non-matching characters. You use it by adding it at the end of the part that should match one or more times (and by default it's greedy, so if there are 5 characters, those 5 will be taken, not 4):
[^0-9A-Za-z]+
I hope this is helpful. Another step would be to also just drop the non-matching characters at the beginning and end, but it's early in the morning and I'm not that fluent with that.
i'v got such string <>1 <>2 <>3
i want remove all '<>' and symbols after '<>' i want replace with such expression like www.test.com/1.jpg, www.test.com/2.jpg, www.test.com/3.jpg
is it possible to do with regex? i only know to find '/<>.?/'
preg_replace('/<>(\d+)/g', 'www.test.com/bla/$1.jpg', $input);
(assuming your replaced elements are just numbers. If they are more general, you'll need to replace '\d+' by something else).
str_replace('<>', 'www.test.com/', $input);
// pseudo code
pre_replace_all('~<>([0-9]+)~', 'www.test.com/$1.jpg', $input);
$string = '<>1 <>2 <>3';
$temp = explode(' ',preg_replace('/<>(\d)/','www.test.com/\1.jpg',$string));
$newString = implode(', ',$temp);
echo $newString;
Based on your example, I don’t think you need regex at all.
$str = '<>1 <>2 <>3';
print_r(str_replace('<>', 'www.test.com/', $str));
Regex's allow you to manipulate a string in any fashion you desire, to modify the string in the fashion you desire you would use the following regex:
<>(\d)
and you would use regex back referencing to keep the values you have captured in your grouping brackets, in this case a single digit. The back reference is typically signified by the $ symbol and then the number of the group you are referencing. As follows:
www.test.com/$1
this would be used in a regex replace scenario which would be implemented in different ways depending on the language you are implementing your regex replace method in.
I have strings in my application that users can send via a form, and they can optionally replace words in that string with replacements that they also specify. For example if one of my users entered this string:
I am a user string and I need to be parsed.
And chose to replace and with foo the resulting string should be:
I am a user string foo I need to be parsed.
I need to somehow find the starting position of what they want to replace, replace it with the word they want and then tie it all together.
Could anyone write this up or at least provide an algorithm? My PHP skills aren't really up to the task :(
Thanks. :)
$result = preg_replace('/\band\b/i', 'foo', $subject);
will find all occurences of and where it's a word on its own and replace it with foo. \b ensures that there is a word boundary before and after and.
use preg_replace. You don't need to think so hard about this though you will have to learn a little bit about regexes. :)
Read up on str_replace, or for more complex replacements on Regular Expressions and preg_replace.
Examples for both:
<?php
$str = 'I am a user string and I need to be parsed.';
echo str_replace( 'and', 'foo', $str ) . "\n";
echo preg_replace( '/and/', 'foo', $str ) . "\n";
?>
In response to the comments of this answer, note that both examples above will replace every occurrence of the search string (and), even when it happens to be within another word.
To take care of that you either have to add the word separators to the str_replace call (see the comment of an example), but this will get quite complicated when you want to take care of all common word separators (space, commas, dots, exclamation marks, question marks etc.).
An easier to way to fix this problem is to use the power of regular expressions and make sure, the actual search string is not found within another word. See Tim Pietzcker's example below for a possible solution.