Question

ok I have this following code for replacing a certain parts of the a big string to something

     $string = 'this <task>post</task> was a <post>post item</post> 
before but now this is now a <task>task item</task> 
and will become like <task>this one</task>';

         $pattern = '^<task>*</task>$';
         $datainmiddle = preg_replace($pattern, $replacement, $string);
         $replacement = strlen(datainmid);
         //I have no idea what to do next...(ノД`)・゜・。

now the thing I want to do here is the following

1. I want to grab each substring in the string that starts with <task> and ends with </task>
2. With each substring I grabbed, I want to grab every data in the middle of the <task> and </task>
3. In every data i grabbed in the middle of the markups I want to measure their length using strlen
4. Now I want to replace every substring that starts with <task> and ends with </task> with the length of their strings in their middles.

the output must be like this

this 4 was a 9 before but now this is now a 9 and will become like 8

If you found it confusing. Please tell it to me

Answer 1

Okay, easy enough:

preg_replace('#<task>(.*?)</task>#e', "strlen('\\1')", $str);

The regex uses (.*?) to start a memory pattern which I later use to pass into strlen().

I’m using .*? to indicate a non-greedy match (otherwise it matches everything between the first <task> and last occurrence of </task>.

The e modifier is used to evaluate the second parameter to preg_replace; this makes it possible to write '\\1' in the expression before it gets evaluated as a whole to return the string length.

Hope that explanation helps a bit to understand the solution.