Chapter 1. Strings [Trimming Blanks from a String]

Chapter 1. Strings

Contents:

Introduction
Accessing Substrings
Replacing Substrings
Processing a String One Character at a Time
Reversing a String by Word or Character
Expanding and Compressing Tabs
Controlling Case
Interpolating Functions and Expressions Within Strings
Trimming Blanks from a String
Parsing Comma-Separated Data
Parsing Fixed-Width Delimited Data
Taking Strings Apart
Wrapping Text at a Certain Line Length
Storing Binary Data in Strings

1.9. Trimming Blanks from a String

1.9.1. Problem

You want to remove whitespace from the beginning or end of a string. For example, you want to clean up user input before validating it.

1.9.2. Solution

Use ltrim( ) , rtrim( ), or trim( ). ltrim( ) removes whitespace from the beginning of a string, rtrim( ) from the end of a string, and trim( ) from both the beginning and end of a string:

$zipcode = trim($_REQUEST['zipcode']);
$no_linefeed = rtrim($_REQUEST['text']);
$name = ltrim($_REQUEST['name']);

1.9.3. Discussion

For these functions, whitespace is defined as the following characters: newline, carriage return, space, horizontal and vertical tab, and null.
Trimming whitespace off of strings saves storage space and can make for more precise display of formatted data or text within <pre> tags, for example. If you are doing comparisons with user input, you should trim the data first, so that someone who mistakenly enters "98052 " as their Zip Code isn't forced to fix an error that really isn't. Trimming before exact text comparisons also ensures that, for example, "salami\n" equals "salami." It's also a good idea to normalize string data by trimming it before storing it in a database.
The trim( ) functions can also remove user-specified characters from strings. Pass the characters you want to remove as a second argument. You can indicate a range of characters with two dots between the first and last characters in the range.

// Remove numerals and space from the beginning of the line
print ltrim('10 PRINT A$',' 0..9');
// Remove semicolon from the end of the line
print rtrim('SELECT * FROM turtles;',';');
PRINT A$
SELECT * FROM turtles

PHP also provides chop( ) as an alias for rtrim( ). However, you're best off using rtrim( ) instead, because PHP's chop( ) behaves differently than Perl's chop( ) (which is deprecated in favor of chomp( ), anyway) and using it can confuse others when they read your code.

1.9.4. See Also

Documentation on trim( ) at http://www.php.net/trim, ltrim( ) at http://www.php.net/ltrim, and rtrim( ) at http://www.php.net/rtrim.