php str_replace and \b word boundary

Question

I am trying to use str_replace, but can\'t figure out how to use \\b for word boundary:

Answer 1

You cannot use \b with str_replace(). The word boundary "\b" is only a valid anchor in regular expressions. So use preg_replace(), it's more appropriate should your search text contain natural language:

 $replace = array_combine($search, $replace);
 preg_replace('#\b('.implode('|',$search).')\b#e', '$replace["$1"]?:"$1"', $str)

Otherwise any occourence of "E" in the text will get replaced with "East". As alternative you could at least add a space right hand to your $search and $replace strings.

Answer 2

Don't bother with the regexes, just order your replacement strings in an order that replaces the longer ones first:

$search = array("North Northeast", "East Northeast", "East Southeast", "South Southeast", "South Southwest", "West Southwest", "West Northwest", "North Northwest", "Northeast", "SouthEast", "Southwest", "Northwest", "North", "East", "South", "West");

$replace = array("NNE", "ENE", "ESE", "SSE", "SSW", "WSW", "WNW", "NNW", "NE", "SE", "SW", "NW", "N", "E", "S", "W");

echo str_replace($search, $replace, "East Northeast winds 20 knots");

// Output: ENE winds 20 knots

This way you don't have to worry about East being replaced before East Southeast.