swap two words in a string php

Question

Suppose there\'s a string \"foo boo foo boo\" I want to replace all fooes with boo and booes with foo. Expected output is \"boo foo boo foo\". What I get is \"foo foo foo fo

Answer 1

$a = "foo boo foo boo";
echo "$a\n";
$a = str_replace("foo", "x", $a);
$a = str_replace("boo", "foo", $a);
$a = str_replace("x", "boo", $a);
echo "$a\n";

note that "x" cannot occur in $a