What are the advantages and disadvantages of using functions like strpos, substr, and str_replace in PHP string manipulation?

When manipulating strings in PHP, functions like strpos, substr, and str_replace can be very useful. strpos helps find the position of a substring within a string, substr extracts a substring based on a start and length, and str_replace replaces occurrences of a substring with another substring. However, these functions may have limitations in certain scenarios such as when dealing with complex patterns or large amounts of data.

// Example of using strpos, substr, and str_replace functions in PHP string manipulation

$string = "Hello, world!";
$substring = "world";
$position = strpos($string, $substring);

if ($position !== false) {
    $newString = substr_replace($string, "PHP", $position, strlen($substring));
    echo $newString;
} else {
    echo "Substring not found in string.";
}