regex - How to replace particular Substring within a String using PHP preg_replace

Question

I am trying to replace word or sequence of words in a string using preg_replace? For example:

Change These:

ABCExample to abcExample
AnotherExample to anotherExample
XyzAbcExample to xyzAbcExample

Leave as it is:

xyzExample to xyzExample 
new to new

Answer 1

You need to use preg_replace_callback function.

$str = <<<EOT
ABCExample
AnotherExample
XyzAbcExample
xyzExample
new
EOT;
echo preg_replace_callback('~(?m)^[A-Za-z]*?(?=(?:[A-Z][a-z]+)+$)~', function ($m)
        { 
            return strtolower($m[0]);
        }, $str);