What are the differences between str_ireplace and preg_replace in PHP for case-insensitive replacement?

When replacing strings in PHP, the str_ireplace function is used for case-insensitive replacements, while preg_replace does not inherently support case-insensitive replacements. To achieve case-insensitive replacements with preg_replace, you can use the "i" modifier in the regular expression pattern.

// Using str_ireplace for case-insensitive replacement
$new_string = str_ireplace("search", "replace", $original_string);

// Using preg_replace with "i" modifier for case-insensitive replacement
$new_string = preg_replace("/search/i", "replace", $original_string);