Question

I’m using php’s preg_replace().

Basically I have 2 possibilities of a string to match:

1. Hello Real World
2. Greetings

Here’s what I wish to accomplish:

1. Hello </span>Real World
2. Gree</span>tings

Rule explained: if a string contains space(s), insert </span> right after the first space character. If a string contains no space(a word), insert </span> right at the middle(+/- if odd character count) of the string.

So far, I have came up with a long working solution:

<?php 
$str = "Hello Real World";
echo preg_match("/ /", $str) ? preg_replace("/ /", " </span>", $str, 1) : preg_replace("/.{" . round(strlen($str)/2) . "}/", "$0</span>", $str, 1);
?>

However, I believe it can be accomplished with a much shorter and elegant regex with only a single preg_replace() call.

Any idea how to do it with only single preg_replace() call? e.g.:

preg_replace("/ |.{" . round(strlen($str)/2) . "}/", "$0</span>", $str, 1)

Answer 1

The regular expression engine doesn’t know ahead of time if there is a space in the string. You don’t need regular expressions to do this at all, although you do need multiple functions:

$pos = strpos($str, ' ');
if ($pos === false) {
   //No space found
   $pos = intval(strlen($str) / 2);
}
else {
   //we want to insert *after* the space
   $pos++;
}
$str = substr_replace($str, '</span>', $pos, 0);