Only the characters listed on this page need to be escaped in PHP regex matching/replacing.

While < and > can act as delimiter, it doesn't need to be escaped in the given example because you already have /(slash) acting as a delimiter.

Referring to the link in question

The preg_quote() function may be used to escape a string for injection into a pattern and its optional second parameter may be used to specify the delimiter to be escaped.

preg_quote should help you, but as @Tomalak said -- why don't you want to use str_replace or something simple (not regexps)?

[\W]+ will match any non-word character.

but to match only the characters from the question, use this:

  $string="sadw$"
  if(preg_match("/[\[^\'£$%^&*()}{@:\'#~?><>,;@\|\\\-=\-_+\-¬\`\]]/", $string)){
   //this string contain atleast one of these [^'£$%^&*()}{@:'#~?><>,;@|\-=-_+-¬`] characters
  }

You can just extract your $link string using sscanf^Docs:

$source = "javascript:window.open('http://www.google.com')";

sscanf($source, "javascript:window.open('%[^']", $link);

echo $link;

(Demo) The benefit is that the syntax is easier to understand than with regular expressions and you can assign values to variables directly.

In case you want to use regular expressions, you need to quote special characters (preg_quote^Docs) before you create your pattern. This needs more work, as you must build the regex pattern prior running it:

# bare pattern, placeholder for matching group:
$pattern = "javascript:window.open('%s')"; 

# quote the pattern, you use ' as delimiter, it needs to be quoted
$pattern = preg_quote($pattern, "'");

# build full regex with delimiters, modifiers and inserting your match group
$pattern = sprintf("'$pattern'is", '(.*?)');

# run it
preg_match($pattern, $source, $export);

Demo

This will result in the following pattern:

'javascript\:window\.open\(\'(.*?)\'\)'is

Or as a valid PHP string:

$pattern = '\'javascript\\:window\\.open\\(\\\'(.*?)\\\'\\)\'is';

or your example:

preg_match('\'javascript\\:window\\.open\\(\\\'(.*?)\\\'\\)\'is', $source, $export);

Just escape it with a backslash \

preg_match_all('/\[Hello\]/', $word, $match); 

print_r($match);

UPD:

Case-insensitive match: (i modifier after delimiter)

preg_match_all('/\[Hello\]/i', $word, $match); 

In many regex implementations, the following rules apply:

Meta characters inside a character class are:

• ^ (negation)
• - (range)
• ] (end of the class)
• \ (escape char)

So these should all be escaped. There are some corner cases though:

• - needs no escaping if placed at the very start, or end of the class ([abc-] or [-abc]). In quite a few regex implementations, it also needs no escaping when placed directly after a range ([a-c-abc]) or short-hand character class ([\w-abc]). This is what you observed
• ^ needs no escaping when it's not at the start of the class: [^a] means any char except a, and [a^] matches either a or ^, which equals: [\^a]
• ] needs no escaping if it's the only character in the class: []] matches the char ]