Is there a canonical function/method for escaping a string to be used in a preg_, such that any special PCRE characters will be interpreted as literal. Basically, a know way to ensure that something like
I am a fancy string (well, that guy ... said I was fancy)
is transformed into
I am a fancy string \(well, that guy \.\.\. said I was fancy\)
The use case is something like
$re = get_string_from_somewhere();
$re = our_magic_function($re);
preg_match_all('%'.$re.'%',$string, $matches);
I believe that preg_quote() is the answer you're looking for...
If you're using a custom delimiter (as you do in your example), be sure to set the second parameter ($delimiter) to the one used in the regex... So your call would be preg_quote($string, '%');
Related
I have some strings containing characters such as \x{1f601} which I want to replace with some text.
When I do this using preg_replace, it would be something like:
preg_replace('/\x{1f601}/u', '######', $str)
However, this doesn't seem to work with str_replace:
str_replace("\x{1f601}", '######', $str)
How can I make such replacements work with str_replace?
preg_replace is a Regex parser/replacer, which is a Perl Regular expression engine, but str_replace is NOT and replaces things with a plaintext method
The Preg_replace you have got can be seen here in regex101, stating that:
matches the character 😁 with position 0x1f601 (128513 decimal or 373001 octal) in the character set
But this could be transferable to a non-regex find and replace,by copy and pasting that face smiley symbol into the str_replace directly.
$str = str_replace("😁", '######', $str)
Or, by reading deceze's comment which gives you a clean, small solution.
Additional:
You are using a character set that is non-standard so it may be useful for you to explore Mb_Str_replace (gitHub) which is an accompanyment (but not directly from) the mb_string collection of PHP functions.
Finally:
Why do you need to do string replace whe you are already doing regex preg_replace? Also please read the manual which states all of this fairly clearly.
Instead of wondering what regex I need for each time I need a regex, I like to learn how to do basic string replacement with regexes.
How do you take one string and replace it with another with regexes in PHP ?
For example how do you take all '/' and replace them with '%' ?
If you just want to do basic string replacement (i.e. replace all 'abc' with '123') then you can use str_replace, which doesn't require using regex. For basic replacements, this will be easier to set up and should run faster.
If you want to use this as a tool to learn regex though (or need more complicated replacements) then preg_replace is the function you need.
You should look into preg_replace. For your question
$string = "some/with/lots/of/slashes";
$new_string = preg_replace("/\//","%",$string);
echo $new_string;
I like to learn how to do basic string replacement with regexes.
That's a little broad for this forum. However, to answer a more specific question like:
For example how do you take all '/' and replace them with '%' ?
You could do that like this:
$result = preg_replace('#\/#', '%', 'Here/is/a/test/string.');
Here is a Rubular that proves the regex.
Note, you are not limited to using the common / delimiter, which means when working with forward slashes it is often easier to change to a different delimiter EG.
$mystring = 'this/is/random';
$result = preg_replace('#/#', '%', $mystring);
This will make '#' the delimiter, rather than the standard '/', so it means you do not need to escape the slash.
I would do this simply with strtr which is very suitable for character mapping, e.g.
strtr('My string has / slashes /', '/', '%');
If you want to also replace the letter a with a dash:
strtr('My string has / slashes /', '/a', '%-');
As you can see, the second and third argument define the transformation map.
Here is the input I am searching:
\u003cspan class=\"prs\">email_address#me.com\u003c\/span>
Trying to just return email_address#me.com.
My regex class=\\"prs\\">(.*?)\\ returns "class=\"prs\">email_address#me.com\" in RegExp which is OK, I can work with that result.
But I can't get it to work in PHP.
$regex = "/class=\\\"prs\\\">(.*?)\\/";
Gives me an error "No ending delimiter"
Can someone please help?
Your original code:
$regex = "/class=\\\"prs\\\">(.*?)\\/";
The reason you get No ending delimiter is that although you are escaping the backslash prior to the closing forward slash, what you have done is escaped it in the context of the PHP string, not in the context of the regex engine.
So the PHP string escaping mechanism does its thing, and by the time the regex engine gets it, it will look like this:
/class=\"prs\">(.*?)\/
This means that the regular expression engine will see the backslash at the end of the expression as escaping the forward slash that you are intending to use to close the expression.
The usual PHP solution to this kind of thing is to switch to using single-quoted string instead of a double-quoted one, but this still won't work, as \\ is an escaped backslash in both single and double quoted strings.
What you need to do is double up the number of backslash characters at the end of your string, so your code needs to look like this:
$regex = "/class=\\\"prs\\\">(.*?)\\\\/";
The way to prove what it's doing is to print the contents of the $regex variable, so you can see what the string will look like to the regex engine. These kinds of errors are actually very hard to spot, but looking at the actual content of the string will help you spot them.
Hope that helps.
If you change to single quotes it should fix it
$regex = '/class=\\\"prs\\\">(.*?)\\/';
I'm new to preg_replace() and I've been trying to get this to work, I couldn't so StackOverflow is my last chance.
I have a string with a few of these:
('pm_IDHERE', 'NameHere');">
I want it to be replaced with nothing, so it would require 2 wildcards for NameHere and pm_IDHERE.
But I've tried it and failed myself, so could someone give me the right code please, and thanks :)
Update:
You are almost there, you just have to make the replacement an empty string and escape the parenthesis properly, otherwise they will be treated as capture group (which you don't need btw):
$str = preg_replace("#\('pm_.+?', '.*?'\);#si", "", $str);
You probably also don't need the modifiers s and i but that is up to you.
Old answer:
Probably str_replace() is sufficient:
$str = "Some string that contains pm_IDHERE and NameHere";
$str = str_replace(array('pm_IDHERE', 'NameHere'), '', $str);
If this is not what you mean and pm_IDHERE is actually something like pm_1564 then yes, you probably need regular expressions for that. But if NameHere has no actual pattern or structure, you cannot replace it with regular expression.
And you definitely have to explain better what kind of string you have and what kind of string you have want to replace.
OK,I know that I should use a DOM parser, but this is to stub out some code that's a proof of concept for a later feature, so I want to quickly get some functionality on a limited set of test code.
I'm trying to strip the width and height attributes of chunks HTML, in other words, replace
width="number" height="number"
with a blank string.
The function I'm trying to write looks like this at the moment:
function remove_img_dimensions($string,$iphone) {
$pattern = "width=\"[0-9]*\"";
$string = preg_replace($pattern, "", $string);
$pattern = "height=\"[0-9]*\"";
$string = preg_replace($pattern, "", $string);
return $string;
}
But that doesn't work.
How do I make that work?
PHP is unique among the major languages in that, although regexes are specified in the form of string literals like in Python, Java and C#, you also have to use regex delimiters like in Perl, JavaScript and Ruby.
Be aware, too, that you can use single-quotes instead of double-quotes to reduce the need to escape characters like double-quotes and backslashes. It's a good habit to get into, because the escaping rules for double-quoted strings can be surprising.
Finally, you can combine your two replacements into one by means of a simple alternation:
$pattern = '/(width|height)="[0-9]*"/i';
Your pattern needs the start/end pattern character. Like this:
$pattern = "/height=\"[0-9]*\"/";
$string = preg_replace($pattern, "", $string);
"/" is the usual character, but most characters would work ("|pattern|","#pattern#",whatever).
I think you're missing the parentheses (which can be //, || or various other pairs of characters) that need to surround a regular expression in the string. Try changing your $pattern assignments to this form:
$pattern = "/width=\"[0-9]*\"/";
...if you want to be able to do a case-insensitive comparison, add an 'i' at the end of the string, thus:
$pattern = "/width=\"[0-9]*\"/i";
Hope this helps!
David