PHP: indicates the earliest version of PHP that supports the function.
| Function | Description | PHP |
|---|---|---|
| addcslashes() | Returns a string with backslashes in front of the specified characters | 4 |
| addslashes() | Returns a string with backslashes in front of predefined characters | 3 |
| bin2hex() | Converts a string of ASCII characters to hexadecimal values | 3 |
| chop() | Alias of rtrim() | 3 |
| chr() | Returns a character from a specified ASCII value | 3 |
| chunk_split() | Splits a string into a series of smaller parts | 3 |
| convert_cyr_string() | Converts a string from one Cyrillic character-set to another | 3 |
| convert_uudecode() | Decodes a uuencoded string | 5 |
| convert_uuencode() | Encodes a string using the uuencode algorithm | 5 |
| count_chars() | Returns how many times an ASCII character occurs within a string and returns the information | 4 |
| crc32() | Calculates a 32-bit CRC for a string | 4 |
| crypt() | One-way string encryption (hashing) | 3 |
| echo() | Outputs strings | 3 |
| explode() | Breaks a string into an array | 3 |
| fprintf() | Writes a formatted string to a specified output stream | 5 |
| get_html_translation_table() | Returns the translation table used by htmlspecialchars() and htmlentities() | 4 |
| hebrev() | Converts Hebrew text to visual text | 3 |
| hebrevc() | Converts Hebrew text to visual text and new lines (\n) into <br /> | 3 |
| html_entity_decode() | Converts HTML entities to characters | 4 |
| htmlentities() | Converts characters to HTML entities | 3 |
| htmlspecialchars_decode() | Converts some predefined HTML entities to characters | 5 |
| htmlspecialchars() | Converts some predefined characters to HTML entities | 3 |
| implode() | Returns a string from the elements of an array | 3 |
| join() | Alias of implode() | 3 |
| levenshtein() | Returns the Levenshtein distance between two strings | 3 |
| localeconv() | Returns locale numeric and monetary formatting information | 4 |
| ltrim() | Strips whitespace from the left side of a string | 3 |
| md5() | Calculates the MD5 hash of a string | 3 |
| md5_file() | Calculates the MD5 hash of a file | 4 |
| metaphone() | Calculates the metaphone key of a string | 4 |
| money_format() | Returns a string formatted as a currency string | 4 |
| nl_langinfo() | Returns specific local information | 4 |
| nl2br() | Inserts HTML line breaks in front of each newline in a string | 3 |
| number_format() | Formats a number with grouped thousands | 3 |
| ord() | Returns the ASCII value of the first character of a string | 3 |
| parse_str() | Parses a query string into variables | 3 |
| print() | Outputs a string | 3 |
| printf() | Outputs a formatted string | 3 |
| quoted_printable_decode() | Decodes a quoted-printable string | 3 |
| quotemeta() | Quotes meta characters | 3 |
| rtrim() | Strips whitespace from the right side of a string | 3 |
| setlocale() | Sets locale information | 3 |
| sha1() | Calculates the SHA-1 hash of a string | 4 |
| sha1_file() | Calculates the SHA-1 hash of a file | 4 |
| similar_text() | Calculates the similarity between two strings | 3 |
| soundex() | Calculates the soundex key of a string | 3 |
| sprintf() | Writes a formatted string to a variable | 3 |
| sscanf() | Parses input from a string according to a format | 4 |
| str_ireplace() | Replaces some characters in a string (case-insensitive) | 5 |
| str_pad() | Pads a string to a new length | 4 |
| str_repeat() | Repeats a string a specified number of times | 4 |
| str_replace() | Replaces some characters in a string (case-sensitive) | 3 |
| str_rot13() | Performs the ROT13 encoding on a string | 4 |
| str_shuffle() | Randomly shuffles all characters in a string | 4 |
| str_split() | Splits a string into an array | 5 |
| str_word_count() | Count the number of words in a string | 4 |
| strcasecmp() | Compares two strings (case-insensitive) | 3 |
| strchr() | Finds the first occurrence of a string inside another string (alias of strstr()) | 3 |
| strcmp() | Compares two strings (case-sensitive) | 3 |
| strcoll() | Locale based string comparison | 4 |
| strcspn() | Returns the number of characters found in a string before any part of some specified characters are found | 3 |
| strip_tags() | Strips HTML and PHP tags from a string | 3 |
| stripcslashes() | Unquotes a string quoted with addcslashes() | 4 |
| stripslashes() | Unquotes a string quoted with addslashes() | 3 |
| stripos() | Returns the position of the first occurrence of a string inside another string (case-insensitive) | 5 |
| stristr() | Finds the first occurrence of a string inside another string (case-insensitive) | 3 |
| strlen() | Returns the length of a string | 3 |
| strnatcasecmp() | Compares two strings using a “natural order” algorithm (case-insensitive) | 4 |
| strnatcmp() | Compares two strings using a “natural order” algorithm (case-sensitive) | 4 |
| strncasecmp() | String comparison of the first n characters (case-insensitive) | 4 |
| strncmp() | String comparison of the first n characters (case-sensitive) | 4 |
| strpbrk() | Searches a string for any of a set of characters | 5 |
| strpos() | Returns the position of the first occurrence of a string inside another string (case-sensitive) | 3 |
| strrchr() | Finds the last occurrence of a string inside another string | 3 |
| strrev() | Reverses a string | 3 |
| strripos() | Finds the position of the last occurrence of a string inside another string (case-insensitive) | 5 |
| strrpos() | Finds the position of the last occurrence of a string inside another string (case-sensitive) | 3 |
| strspn() | Returns the number of characters found in a string that contains only characters from a specified charlist | 3 |
| strstr() | Finds the first occurrence of a string inside another string (case-sensitive) | 3 |
| strtok() | Splits a string into smaller strings | 3 |
| strtolower() | Converts a string to lowercase letters | 3 |
| strtoupper() | Converts a string to uppercase letters | 3 |
| strtr() | Translates certain characters in a string | 3 |
| substr() | Returns a part of a string | 3 |
| substr_compare() | Compares two strings from a specified start position (binary safe and optionally case-sensitive) | 5 |
| substr_count() | Counts the number of times a substring occurs in a string | 4 |
| substr_replace() | Replaces a part of a string with another string | 4 |
| trim() | Strips whitespace from both sides of a string | 3 |
| ucfirst() | Converts the first character of a string to uppercase | 3 |
| ucwords() | Converts the first character of each word in a string to uppercase | 3 |
| vfprintf() | Writes a formatted string to a specified output stream | 5 |
| vprintf() | Outputs a formatted string | 4 |
| vsprintf() | Writes a formatted string to a variable | 4 |
| wordwrap() | Wraps a string to a given number of characters | 4 |
Information courtesy: W3Schools.com
Please don’t link to w3schools, especially for their crypt() article. It mistakenly refers to hashing as encryption and has been a source of severe misery to anyone trying to teach people better habits.