how to swap variable text with another text php code example

Example 1: str_replace php variable

$var1 = 'hello.world';
$var2 = str_replace(".", "-", $var1);
echo $var2; // hello-world

Example 2: php str replace

<?php
$string = str_ireplace("FoX", "CAT", "the quick brown fox jumps over the lazy dog");
echo $string; // the quick brown CAT jumps over the lazy dog
?>