What is the significance of the backslash in the regular expression pattern used in the code snippet?

The backslash in a regular expression pattern is used to escape special characters, such as the dot (.), which has a special meaning in regular expressions. To match a literal dot in a string using a regular expression, you need to escape it with a backslash. In the provided code snippet, the backslash is used before the dot to match a literal dot in the input string.

$input = "This is a sentence with a dot.";
$pattern = "/\./";
if (preg_match($pattern, $input)) {
    echo "Found a dot in the input string.";
} else {
    echo "No dot found in the input string.";
}