How can I get matches when using preg_replace in PHP?

Question

I am trying to capture uppercase letters from several words and wrap them in span tags. I use preg_replace to extract and wrap, but it doesn’t output anything.

preg_replace("/[AZ]/", "<span class=\"initial\">$1</span>", $str) 

Answer 1

You need to put the pattern in parentheses /([AZ])/ , for example:

 preg_replace("/([AZ])/", "<span class=\"initial\">$1</span>", $str) 

Answer 2

\0 will also match the entire matched expression without explicit capture using parentheses.

 preg_replace("/[AZ]/", "<span class=\"initial\">\\0</span>", $str) 

As always, you can go to php.net/preg_replace or php.net/<whatever search term> quickly find documentation. Print the documentation:

\ 0 or $ 0 refers to the text matched by the entire pattern.

Answer 3

From the preg_replace documentation on php.net :

the replacement may contain links to the form \ n or (starting with PHP 4.0.4) $ n, with the latter form being preferred. Each such link will be replaced by text captured in the nth bracket.

See Flubba example.

Answer 4

Use brackets around the desired grip.