str_replace for distinct word

Question

suppose I have $str=\"nikparsa neginnikparsa somenikparsa\" when I use

$str= str_replace(\'nikparsa\', \'nik parsa\', $str);
echo $str;

Answer 1

Well, if you really don't want to use preg_replace, then:

substr( str_replace( ' stackoverflow ', '  do you see the apples?  ', " $str "), 1, -1 );

Read the comments about its limitations :)

Answer 2

Use preg_replace:

$str = preg_replace('/\bnikparsa\b/i', 'nik parsa', $str);