Learning PHP, MySQL, and JavaScript

Using printf

You’ve already seen the print and echo functions, which simply output text to the browser. But a much more powerful function, printf, controls the format of the output by letting you put special formatting characters in a string.

For each formatting character, printf expects you to pass an argument that it will display using that format. For instance, the following example uses the %d conversion specifier to display the value 3 in decimal:

printf("There are %d items in your basket", 3);

If you replace the %d with %b, the value 3 would be displayed in binary (11). Table 7-1 shows the conversion specifiers supported.

Table 7-1. The printf conversion specifiers

Specifier	Conversion action on argument arg	Example (for an arg of 123)
%	Display a % character (no arg is required)	%
b	Display arg as a binary integer	1111011
c	Display ASCII character for the arg	{
d	Display arg as a signed decimal integer	123
e	Display arg using scientific notation	1.23000e+2
f	Display arg as floating point	123.000000
o	Display arg as an octal integer	173
s	Display arg as a string	123
u	Display arg as an unsigned decimal	123
x	Display arg in lowercase hexadecimal	7b
X	Display arg in uppercase hexadecimal	7B

You can have as many specifiers as you like in a printf function, as long as you pass a matching number of arguments, and as long as each specifier is prefaced by a % symbol. Therefore the following code is valid, and will output “My name is Simon. I’m 33 years old, which is 21 in hexadecimal”:

printf("My name is %s. I'm %d years ...