What are the potential pitfalls of using functions like strstr() and strchr() to extract specific parts of a string in PHP?

Using functions like strstr() and strchr() can be problematic when dealing with strings that may contain special characters or multibyte characters. These functions work based on byte values, so they may not handle multibyte characters correctly, leading to unexpected results. To avoid this issue, it's recommended to use multibyte string functions like mb_strpos() and mb_substr() when working with strings that may contain multibyte characters.

// Using mb_strpos() and mb_substr() to extract specific parts of a string
$string = "Hello, 你好";
$position = mb_strpos($string, ",");
if ($position !== false) {
    $substring = mb_substr($string, $position + 1);
    echo $substring; // Output: 你好
}