sprintf、printf输出格式化字符串。

比如sprintf()的函数原型如下：

string sprintf ( string $format [, mixed $args [, mixed $... ]] )

其中$format用于指定输出的字符串的格式。

进过总结$format遵守以下原型：

%[n$][flags][width][.precision]specifier

其中：

•  n$　　　　是position specifier，指明本占位符代表的是哪个参数
  

  <?php$num = 5;$location = ‘tree‘;$format = ‘The %2$s contains %1$d monkeys‘;echo sprintf($format, $num, $location);

   

• flags　　　　是一些标志，用来表明是否显示+号、填充字符、对齐方式。具体flags见下表
  

  flag	描述
  +	默认情况下，只有在数字为负数时，才会显示出符号位‘-’。如果数字为正数，则不显示符号位‘+’。本flag设置之后，不论数字为正或为负，都显示符号位。
  ‘sign 或者 0	本flag用来设置用来填充的符号。填充符号是为了是输出的字符串达到width指定的长度。默认的填充符是空格。标准的指定填充符的方式是：单引号+填充符，不过对于0作为填充符，即 可以使用标准定义，也可以直接申明。
  -	本flag用来指明输出的结果是左对齐还是右对齐。缺省下是右对齐，申明本flag后，为左对齐。

  
  

  <?phpecho sprintf ("|%+4d|%+4d|\n",   1, -1);echo sprintf ("|%-4d|%-4d|\n",   1, -1);echo sprintf ("|%+-4d|%+-4d|\n", 1, -1);/*outputs:|  +1|  -1||1   |-1  ||+1  |-1  |*/echo sprintf ("|%04d|\n",   -2);echo sprintf ("|%‘:4d|\n",  -2);echo sprintf ("|%-‘:4d|\n", -2);/*outputs:|-002||::-2||-2::|*/

• width　　　　指明本格式输出至少有多少字符。即指明字符的输出长度。见上例。
• .precision　　指明对于浮点数，应该保留几位小数
  

  <?php$money = 123.1234;echo sprintf("%.2f", $money);    //123.1

• specifier　　specifier指明应该将参数以何种参数类型对待。
  
  

  <?php$n =  43951789;$u = -43951789;$c = 65; // ASCII 65 is ‘A‘// notice the double %%, this prints a literal ‘%‘ characterprintf("%%b = ‘%b‘\n", $n); // binary representationprintf("%%c = ‘%c‘\n", $c); // print the ascii character, same as chr() functionprintf("%%d = ‘%d‘\n", $n); // standard integer representationprintf("%%e = ‘%e‘\n", $n); // scientific notationprintf("%%u = ‘%u‘\n", $n); // unsigned integer representation of a positive integerprintf("%%u = ‘%u‘\n", $u); // unsigned integer representation of a negative integerprintf("%%f = ‘%f‘\n", $n); // floating point representationprintf("%%o = ‘%o‘\n", $n); // octal representationprintf("%%s = ‘%s‘\n", $n); // string representationprintf("%%x = ‘%x‘\n", $n); // hexadecimal representation (lower-case)printf("%%X = ‘%X‘\n", $n); // hexadecimal representation (upper-case)printf("%%+d = ‘%+d‘\n", $n); // sign specifier on a positive integerprintf("%%+d = ‘%+d‘\n", $u); // sign specifier on a negative integer%b = ‘10100111101010011010101101‘%c = ‘A‘%d = ‘43951789‘%e = ‘4.39518e+7‘%u = ‘43951789‘%u = ‘4251015507‘%f = ‘43951789.000000‘%o = ‘247523255‘%s = ‘43951789‘%x = ‘29ea6ad‘%X = ‘29EA6AD‘%+d = ‘+43951789‘%+d = ‘-43951789‘

  View Code
  
  
  

  specifier	Output	Example
  d	Signed decimal integer	392
  u	Unsigned decimal integer	7235
  o	Unsigned octal	610
  x	Unsigned hexadecimal integer	7fa
  X	Unsigned hexadecimal integer (uppercase)	7FA
  f	Decimal floating point, lowercase	392.65
  F	Decimal floating point, uppercase	392.65
  e	Scientific notation (mantissa/exponent), lowercase	3.9265e+2
  E	Scientific notation (mantissa/exponent), uppercase	3.9265E+2
  g	Use the shortest representation: %e or %f	392.65
  G	Use the shortest representation: %E or %F	392.65
  c	the argument is treated as an integer, and presented as the character with that ASCII value	a
  s	String of characters	sample
  p	the argument is treated as an integer, and presented as a binary number	10100011
  %	A % followed by another % character will write a single % to the stream.	%

  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  

   

  
  
   注明：
  本文主要参考官方文档：http://php.net/manual/en/function.sprintf.php 。并对文档进行了总结，以及对文档部分有偏差部分的纠正。不同处如下：
  1. flags可以是无序的。并不像文档所说——需要按照固定的顺序。flags处的例子可以说明问题。（另外需要指出的是：填充符0和左对齐标志‘-’合用会产生意想不到的结果，见下面的例子）

  echo sprintf ("|%-04d|\n",  -2);　　//输出：     |-2  |

PHP中sprintf、printf等字符串格式化输出中的格式规则总结