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.
Specifier | Conversion action on argument arg | Example (for an arg of 123) |
| Display a % character (no
|
|
| Display |
|
| Display ASCII character
for the |
|
| Display |
|
| Display |
|
| Display |
|
| Display |
|
| Display |
|
| Display |
|
| Display |
|
| Display |
|
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 ...