不匹配括号中的字符串php正则表达式

Question

I've been trying to use preg_replace() in php to replace string. I want to match and replace all 's' in this string, but I just came with solution only mathching 's' between 'b' and 'c' or 's' between > <. Is there any way I can use negative look behind not just for the character '>' but for whole string ? I don't want to replace anything in brackets.

     <text size:3>s<text size:3>absc
     <text size:3>xxetxx<text size:3>sometehing

edit: just get 's' in >s< and in bsc. Then when I will change string for example from 's' to 'te', to replace 'te' in xtex and sometehing. So I was looking for regular expression to avoid replacing anything in <....>

Answer 1

You can use this pattern:

$pattern = '/((<[^>]*>)*)([^s]*)s/';
$replace = '\1\3■';                                      # ■ = your replacement string

$result = preg_replace( $pattern, $replace, $str );

regex101 demo

Pattern explanation:

(               # group 1:
(<[^>]*>)*      # group 2: zero-or-more <...>
)    
([^s]*)         # group 3: zero-or-more not “s”
s               # litterally “s”

If you want match case-insensitive, add a “i” at the end of pattern:

$pattern = '/((<[^>]*>)*)([^s]*)s/i';

Edit: Replacement explanation

In the search pattern we have 3 groups surrounded by round brackets. In the replace string we can refer to groups by syntax \\1 , where 1 is the group number.

So, replace string in the example means: replace group 1 with itself, replace group 3 with itself, replace “s” with desired replacement. We don't need to use group 2 because it is included in group 1 (this due to regex impossibility to retrieve repeating groups).

In the demo string:

abs<text size:3>ssss<text size:3><img src="img"><text size:3>absc
└┘╵└───────────┘╵╵╵╵└───────────────────────────────────────┘└┘╵╵
└─┘└────────────┘╵╵╵└──────────────────────────────────────────┘
 1  2            345 6

Pattern matches:

     group 1    group 3       s
    ---------  ---------  ---------
1 >     0          1          1
2 >     1          0          1
3 >     0          0          1
4 >     0          0          1
5 >     0          0          1    
6 >     3          1          1

The last “c” is not matches, so is not replaced.

Answer 2

Use preg_match_all to get all the s letters and use it with flag PREG_OFFSET_CAPTURE to get the indices.

The regular expression $pat contains a negative lookahead and lookbehind so that the s inside the brackets expression is not matched.

In this example I replace s with the string 5 . Change to the string you want to substitute:

<?php

$s = " <text size:3>s<text size:3>absc";
$pat = "/(?<!\<text )s(?!ize:3\>)/";

preg_match_all($pat, $s, $matches, PREG_OFFSET_CAPTURE);

foreach ($matches[0] as $match) {
    $s[$match[1]] = "5";
}

print_r(htmlspecialchars($s));