定义和用法

pack() 函数把数据装入一个二进制字符串。

pack(format,args+)

format 必需。规定在包装数据时所使用的格式。

args+ 可选。规定被包装的一个或多个参数。

format 参数的可能值：

• 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)
• f - float (machine dependent size and representation)
• d - double (machine dependent size and representation)
• x - NUL byte
• X - Back up one byte
• @ - NUL-fill to absolute position

例子

<?php
echo pack("C3",80,72,80);
?>

输出：PHP

<?php
echo pack("C*",80,72,80);
?>

输出：PHP