What are the potential issues with using eregi_replace in PHP and what are the modern alternatives?

The eregi_replace function in PHP is deprecated as of PHP 5.3.0 and removed in PHP 7.0.0 due to performance and security issues. It is recommended to use the preg_replace function with the 'i' modifier for case-insensitive matching as a modern alternative.

// Using preg_replace as a modern alternative to eregi_replace
$string = "Hello, World!";
$pattern = "/hello/i";
$replacement = "Hi";
$result = preg_replace($pattern, $replacement, $string);
echo $result; // Output: Hi, World!