- Listing of String Functions
- Using the String Functions
- Formatting Strings
- Converting to and from Strings
- Creating Arrays
- Modifying Arrays
- Removing Array Elements
- Looping Over Arrays
- Listing of the Array Functions
- Sorting Arrays
- Navigating through Arrays
- Imploding and Exploding Arrays
- Extracting Variables from Arrays
- Merging and Splitting Arrays
- Comparing Arrays
- Manipulating the Data in Arrays
- Creating Multidimensional Arrays
- Looping Over Multidimensional Arrays
- Using the Array Operators
- Summary
This chapter is from the book
This chapter is from the book
This chapter is from the book
Formatting Strings
There's a pair of string functions that are particularly useful when you want to format data for display (such as when you're formatting numbers in string form): printf and sprintf. The printf function echoes text directly, and you assign the return value of sprintf to a string. Here's how you use these functions (items in square brackets, [ and ], in function specifications like this one are optional):
printf (format [, args]) sprintf (format [, args])
The format string is composed of zero or more directives: characters that are copied directly to the result, and conversion specifications. Each conversion specification consists of a percent sign (%), followed by one or more of these elements, in order:
- An optional padding specifier that indicates which character should be used to pad the results to the correct string size. This may be a space character or a 0 (zero character). The default is to pad with spaces.
- An optional alignment specifier that indicates whether the results should be left- justified or right-justified. The default is right-justified (a - character here will make it left-justified).
- An optional number, the width specifier, specifying how many characters (minimum) this conversion should result in.
- An optional precision specifier that indicates how many decimal digits should be displayed for floating-point numbers. (There is no effect for types other than float.)
- A type specifier that says what type the argument data should be treated as.
Here are the possible type specifiers:
|
% |
A literal percent character. No argument is required. |
|
b |
The argument is treated as an integer, and presented as a binary number. |
|
c |
The argument is treated as an integer, and presented as the character with that ASCII value. |
|
d |
The argument is treated as an integer, and presented as a (signed) decimal number. |
|
u |
The argument is treated as an integer, and presented as an unsigned decimal number. |
|
f |
The argument is treated as a float, and presented as a floating-point number. |
|
- |
The argument is treated as an integer, and presented as an octal number. |
|
s |
The argument is treated as and presented as a string. |
|
x |
The argument is treated as an integer and presented as a hexadecimal number (with lowercase letters). |
|
X |
The argument is treated as an integer and presented as a hexadecimal number (with uppercase letters). |
These functions take a little getting used to, especially when you're formatting floating point values. For example, a format specifier of %6.2 means that a floating point number will be given six places in the display, with two places behind the decimal point. Here's an example that puts printf and sprintf to work:
<?php
printf("I have %s apples and %s oranges.\n", 4, 56);
$year = 2005;
$month = 4;
$day = 28;
printf("%04d-%02d-%02d\n", $year, $month, $day);
$price = 5999.99;
printf("\$%01.2f\n", $price);
printf("%6.2f\n", 1.2);
printf("%6.2f\n", 10.2);
printf("%6.2f\n", 100.2);
$string = sprintf("Now I have %s apples and %s oranges.\n", 3, 5);
echo $string;
?>
In this example, we're formatting simple integers as strings, aligning floating-point numbers vertically so the decimal point lines up, and so on. Here's what you see when you run this script at the command line:
I have 4 apples and 56 oranges. 2005-04-28 $5999.99 1.20 10.20 100.20 Now I have 3 apples and 5 oranges.