# PHP pack/unpack reference

| Code | Description                                                  |
| ---- | ------------------------------------------------------------ |
| a    | NUL-padded string                                            |
| A    | SPACE-padded string                                          |
| h    | Hex string, low nibble first                                 |
| H    | Hex string, high nibble first                                |
| c    | signed char                                                  |
| C    | unsigned char                                                |
| s    | signed short (always 16 bit, machine byte order)             |
| S    | unsigned short (always 16 bit, machine byte order)           |
| n    | unsigned short (always 16 bit, big endian byte order)        |
| v    | unsigned short (always 16 bit, little endian byte order)     |
| i    | signed integer (machine dependent size and byte order)       |
| I    | unsigned integer (machine dependent size and byte order)     |
| l    | signed long (always 32 bit, machine byte order)              |
| L    | unsigned long (always 32 bit, machine byte order)            |
| N    | unsigned long (always 32 bit, big endian byte order)         |
| V    | unsigned long (always 32 bit, little endian byte order)      |
| q    | signed long long (always 64 bit, machine byte order)         |
| Q    | unsigned long long (always 64 bit, machine byte order)       |
| J    | unsigned long long (always 64 bit, big endian byte order)    |
| P    | unsigned long long (always 64 bit, little endian byte order) |
| f    | float (machine dependent size and representation)            |
| g    | float (machine dependent size, little endian byte order)     |
| G    | float (machine dependent size, big endian byte order)        |
| d    | double (machine dependent size and representation)           |
| e    | double (machine dependent size, little endian byte order)    |
| E    | double (machine dependent size, big endian byte order)       |
| x    | NUL byte                                                     |
| X    | Back up one byte                                             |
| Z    | NUL-terminated (ASCIIZ) string, will be NUL padded           |
| @    | NUL-fill to absolute position                                |