What are the potential issues with using deprecated PHP functions like eregi and split in web development?

Using deprecated PHP functions like eregi and split in web development can lead to security vulnerabilities and compatibility issues with newer versions of PHP. To solve this problem, you should replace these deprecated functions with their modern equivalents, such as preg_match and explode.

// Before
if (eregi('pattern', $string)) {
    $parts = split('delimiter', $string);
}

// After
if (preg_match('/pattern/i', $string)) {
    $parts = explode('delimiter', $string);
}