如何在php中使用preg删除字符串的一部分？

Question

I want to take out GP123 (a string consisting of digits and characters in any order) from a bigger string ($str) and exclude Hello ($str1) which will be a string in another variable. My code is this. But it is not working. How can I remove a part of a string.

$str=" HelloGP123";
$str1="Hello";
preg_match_all("/(?:$str1)\w+\d+\w+/",$str,$str2);
print_r($str2); 

Answer 1

Well My need was just to erase $str1(Hello) part from $str (HelloGP123) and store final remainder in $str2. And I was going all around Regular Expression.

But I realized this can be solved in a much easier way by string replacement. So here is what I did and it worked.

$str2= str_ireplace($str1, '', $str);

I guess this is the most easiest method than storming our brain by trying various combinations of regex.