Find substring with specific string pattern in php

Question

I want to find substring in a string with ___string_string___ pattern where string_string can be any string.

$string = "This string contains ___MY_VALUE___ which I want to replace and there is also ___ONE_MORE_VALUE___ which I want to replace";`

It is not clear what your `string` part may contain. Please provide the requirements. An example code/regex showing what you tried would also help clearing that out. — Wiktor Stribiżew, Feb 15 '17 at 09:48
I want to fetch strings with ___value___ pattern and then replace with other value. e.g: There will be string "This is my ___OTP___" then I will replace ___OTP___ with value like 1234, but there can be multiple __OTP1__,__OTP2__ in a string and I wanted to replace all with different values. — Ganesh Sawant, Feb 15 '17 at 09:49
Possible duplicate of [How to check if one string contains another substring in JavaScript?](http://stackoverflow.com/questions/1789945/how-to-check-if-one-string-contains-another-substring-in-javascript) — Kindle Q, Feb 15 '17 at 09:51
Possible duplicate of [How do I check if a string contains a specific word in PHP?](http://stackoverflow.com/questions/4366730/how-do-i-check-if-a-string-contains-a-specific-word-in-php) — pringi, Feb 15 '17 at 10:06

Tom · Answer 1 · 2017-02-15T10:11:43.170

1

Provided you simply want a string & underscores, and nothing else, in between the ___'s, then;

/___([a-zA-Z_]*)___/m

Here's the working example

Edit

To fix the false positive on ______, I've added a positive lookahead, and made a couple of other tweaks.

/_{3}(?=.*[a-zA-Z_])(.*[a-zA-Z_])_{3}/m

_{3} - Matches 3 underscores

(?=.*[a-zA-Z_]) - Positive lookahead to make sure one of these characters is present

(.*[a-zA-Z_]) - The actual matching group

_{3} - And match the ending 3 underscores

Here's a working example of this second version

edited Feb 15 '17 at 10:11

answered Feb 15 '17 at 09:51

Tom

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1

this will also match `_________` – RomanPerekhrest Feb 15 '17 at 09:52

score 1 · Answer 2 · answered Feb 15 '17 at 09:58

Try this using preg_replace_callback():

$string = "This string contains ___MY_VALUE___ which I want to replace and there is also ___ONE_MORE_VALUE___ which I want to replace";

$replaced = preg_replace_callback("/\___([a-zA-Z_]*)\___/", function($m){
    return "(replaced {$m[1]})";
}, $string);


print_r($replaced);

score 1 · Accepted Answer · answered Feb 15 '17 at 10:04

The solution using preg_replace_callback with specific regex pattern:

// custom replacement list
$pairs = ['___MY_VALUE___' => 123, '___ONE_MORE_VALUE___' => 456];
$str = '"This string contains ___MY_VALUE___ which I want to replace and there is also ___ONE_MORE_VALUE___ which I want to replace";';

$str = preg_replace_callback('/___(([a-z]+_?)+)___/mi', function($m) use($pairs){
    return (isset($pairs[$m[0]]))? $pairs[$m[0]] : $m[0];
}, $str);

print_r($str);

The output:

"This string contains 123 which I want to replace and there is also 456 which I want to replace";

score 0 · Answer 4 · answered Feb 15 '17 at 10:24

To replace everything that is not 3 underscores in between two "3 underscores", use this regex:

/___((?:(?!___).)+)___/

To replace "keywords" with corresponding values, use preg_replace_callback like that:

$replace = array(
'MY_VALUE' => '**Replacement of MY_VALUE**',
'ONE_MORE_VALUE' => '**Replacement of ONE_MORE_VALUE**',
' third value to be replaced ' => '**Replacement of  third value to be replaced**',
);

$string = "This string contains ___MY_VALUE___ which I want to replace 
    and there is also ___ONE_MORE_VALUE___ which I want to replace. 
    This is the ___ third value to be replaced ___";

$string = preg_replace_callback('/___((?:(?!___).)+)___/', 
            function ($m) use($replace){
                return $replace[$m[1]];
            }
            , $string);
echo $string,"\n";

Output:

This string contains **Replacement of MY_VALUE** which I want to replace 
and there is also **Replacement of ONE_MORE_VALUE** which I want to replace. 
This is the **Replacement of  third value to be replaced**

Find substring with specific string pattern in php

4 Answers4