What is the function that can be used in PHP to replace characters in a string?

To replace characters in a string in PHP, you can use the `str_replace()` function. This function takes three parameters: the character or characters you want to replace, the character or characters you want to replace them with, and the string in which you want to make the replacements. The function will return a new string with the specified replacements made.

// Example of using str_replace function to replace characters in a string
$string = "Hello, World!";
$new_string = str_replace("o", "0", $string);
echo $new_string; // Output: Hell0, W0rld!