addslashes() - Add backslashes (\) base_convert() - Converts a number between two bases crc32() - Cyclic redundancy checksum crypt() - Calculate the hash of a string decbin() - Convert numbers to binary (base-2) decoct() - Convert numbers to octal (base-8) dechex() - Convert numbers to hexadecimal (base-16) dns_get_record() - Retrieves DNS resource htmlspecialchars() - Convert special characters to HTML entities lcfirst() - Converts first character to lowercase md5() - Calculate MD5 hash of a string openssl_encrypt() - Encrypts plain text data openssl_decrypt() - Decrypts cipher text openssl_get_cipher_methods() - Lists available cipher methods preg_match() - Regular expression (RegEx) match sha1() - Calculate sha1 hash of a string str_word_count() - Determines number of words in a string strlen() - Calculate character length of a string strip_tags() - Removes HTML and PHP tags from a string stripslashes() - Removes backslashes (\) strrev() - Reverses order of a string strtolower() - Convert string to all lowercase strtoupper() - Convert string to all uppercase ucfirst() - Converts first character to uppercase ucwords() - Converts first letter of each word to uppercase urlencode() - Encodes a string for use in URL query urldecode() - Decodes the query part of a URL string.