What is the recommended PHP function to check if one string is contained within another string?

To check if one string is contained within another string in PHP, you can use the `strpos()` function. This function searches for a specific substring within a string and returns the position of the first occurrence of the substring. If the substring is not found, `strpos()` will return `false`.

$haystack = "Hello, World!";
$needle = "World";

if (strpos($haystack, $needle) !== false) {
    echo "The needle is found in the haystack.";
} else {
    echo "The needle is not found in the haystack.";
}