PHP outputs formatted string function printf()

Possible format values:

• %% - returns a percent sign %

• %b - a binary number

• %c - the character corresponding to the ASCII value

• %d - the decimal number containing the sign (negative, 0, positive)

• %e - Use lowercase scientific notation (e.g. 1.2e+2)

• ##%E - Use uppercase scientific notation (e.g. 1.2E+ 2)

• %u - Decimal number without sign (greater than or equal to 0)

• %f - Floating point number (local setting) )

• %F - floating point number (non-native setting)

##%g - shorter %e and %f
%G - shorter %E and %f

• ##%o - octal number

• %s - character String

• %x - Hexadecimal number (lowercase letters)

• ##%X - Hexadecimal number (uppercase letters)

• Additional format value. Must be placed between % and a letter (e.g. %.2f):

+ (Add + or - in front of a number to define the sign of the number. By default, only Negative numbers are marked, positive numbers are not marked)

• ' (Specifies what to use as padding, the default is spaces. It must be used with the width specifier. For example: %'x20s ( Use "x" as padding))

• - (Adjust the variable value left)

• [0-9] (Specify the minimum variable value Width)

• .[0-9] (Specifies the number of decimal places or the maximum string length)

• Note: If you use more than one of the above The format values ​​must be used in the order above and cannot be disrupted.

技术细节

返回值： 返回被输出字符串的长度。

PHP 版本： 4+

更多实例

实例 1

使用格式值 %f：

<?php
$number = 123;
printf("%f",$number);
?>

实例 2

使用占位符：

<?php
$number = 123;
printf("With 2 decimals: %1$.2f
<br>With no decimals: %1$u",$number);
?>

实例 3

所有可能的格式值的演示：

<?php
$num1 = 123456789;
$num2 = -123456789;
$char = 50; // The ASCII Character 50 is 2

// Note: The format value "%%" returns a percent sign
printf("%%b = %b <br>",$num1); // Binary number
printf("%%c = %c <br>",$char); // The ASCII Character
printf("%%d = %d <br>",$num1); // Signed decimal number
printf("%%d = %d <br>",$num2); // Signed decimal number
printf("%%e = %e <br>",$num1); // Scientific notation (lowercase)
printf("%%E = %E <br>",$num1); // Scientific notation (uppercase)
printf("%%u = %u <br>",$num1); // Unsigned decimal number (positive)
printf("%%u = %u <br>",$num2); // Unsigned decimal number (negative)
printf("%%f = %f <br>",$num1); // Floating-point number (local settings aware)
printf("%%F = %F <br>",$num1); // Floating-point number (not local settings aware)
printf("%%g = %g <br>",$num1); // Shorter of %e and %f
printf("%%G = %G <br>",$num1); // Shorter of %E and %f
printf("%%o = %o <br>",$num1); // Octal number
printf("%%s = %s <br>",$num1); // String
printf("%%x = %x <br>",$num1); // Hexadecimal number (lowercase)
printf("%%X = %X <br>",$num1); // Hexadecimal number (uppercase)
printf("%%+d = %+d <br>",$num1); // Sign specifier (positive)
printf("%%+d = %+d <br>",$num2); // Sign specifier (negative)
?>

实例 4

字符串说明符的演示：

<?php
$str1 = "Hello";
$str2 = "Hello world!";

printf("[%s]<br>",$str1);
printf("[%8s]<br>",$str1);
printf("[%-8s]<br>",$str1);
printf("[%08s]<br>",$str1); 
printf("[%&#39;*8s]<br>",$str1);
printf("[%8.8s]<br>",$str2); 
?>

printf()函数优点在于可以格式化输出!

printf的格式控制的完整格式：

% - 0 m.n l或h 格式字符

下面对组成格式说明的各项加以说明：

①%：表示格式说明的起始符号，不可缺少。

②-：有-表示左对齐输出，如省略表示右对齐输出。

③0：有0表示指定空位填0,如省略表示指定空位不填。

④m.n：m指域宽，即对应的输出项在输出设备上所占的字符数。N指精度。用于说明输出的实型数的小数位数。为指定n时，隐含的精度为n=6位。

⑤l或h:l对整型指long型，对实型指double型。h用于将整型的格式字符修正为short型。

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