String Theory - A Quick Trim (
Page 6 of 7 )
If you're looking to
perform a little cosmetic surgery on your strings, a good place to start is the
family of trim() functions. The most useful of these, trim(), is constructed
specifically to remove whitespace from the beginning and end of a string. This
comes in handy if you need to remove whitespace from a value prior to using it
elsewhere (a database insert, maybe?)
<?
$str = " ever seen a white pigeon?";
// returns "ever seen a white pigeon?"
echo trim($str);
?>
It's also a good idea to use the trim() function on data
entered into online forms, in order to ensure that your error-checking routines
don't miss entries containing only whitespace. Here's an example which
illustrates what I mean:
<?
$search = " ";
// bad code, will not identify that search string
// actually contains nothing
if ($search != "")
{
perform_search();
}
// good code, will account for whitespace-only entries
if (trim($search) != "")
{
perform_search();
}
?>
You can also use the ltrim() and rtrim() functions, which
remove whitespace from the beginning and end of a string
respectively.
The next few string functions come in very handy when
adjusting the case of a text string from lower- to upper-case, or
vice-versa:
strtolower() - convert string to lower case strtoupper()-
convert string to upper case ucfirst() - convert the first character of string
to upper case ucwords() - convert the first character of each word in string to
upper case
Here's an example:
<?
$str = "Something's rotten in the state of Denmark";
// returns "something's rotten in the state of denmark"
echo strtolower($str);
// returns "SOMETHING'S ROTTEN IN THE STATE OF DENMARK"
echo strtoupper($str);
// returns "Something's rotten in the state of Denmark"
echo ucfirst($str);
// returns "Something's Rotten In The State Of Denmark"
echo ucwords($str);
?>
You've already used the print() function extensively to
display output. However, the print() function doesn't allow you to format output
in any significant manner - for example, you can't write 1000 as 1,000 or 1 as
00001. And so the clever PHP developers came up with the sprintf() function,
which allows you to define the format in which data is output.
Consider
the following example:
<?
// returns 1.6666666666667
print(5/3);
?>
As you might imagine, that's not very friendly. Ideally,
you'd like to display just the "significant digits" of the result. And so, you'd
use the sprintf() function:
<?
// returns 1.67
echo sprintf("%1.2f", (5/3));
?>
A quick word of explanation here: the PHP sprintf() function
is very similar to the printf() function that C programmers are used to. In
order to format the output, you need to use "field templates", templates which
represent the format you'd like to display.
Some common field templates
are:
%s string
%d decimal number
%x hexadecimal number
%o octal
number
%f float number
You can also combine these field templates with
numbers which indicate the number of digits to display - for example, %1.2f
implies that PHP should only display two digits after the decimal point. If
you'd like the formatted string to have a minimum length, you can tell PHP which
character to use for padding by prefixing it with a single quote
(').
Here are a few more examples of sprintf() in action:
<?
// returns 00003
echo sprintf("%05d", 3);
// returns $25.99
echo sprintf("$%2.2f", 25.99);
// returns ****56
echo sprintf("%'*6d", 56);
?>
In addition to the sprintf() function, PHP also offers the
strpad() function, which is used for padding strings to a specific length. This
function accepts a string or string variable as argument, together with the
minimum string length required; a couple of optional arguments allow you to also
specify which character to use for padding, and the direction in which padding
is to take place.
Here are a couple of examples:
<?
$str = "da bomb";
// returns "da bomb "
echo str_pad($str, 10);
// returns "da bomb###"
echo str_pad($str, 10, "#");
// returns "***da bomb"
echo str_pad($str, 10, "*", STR_PAD_LEFT);
?>
Finally, the wordwrap() function can be used to break long
sentences at a specified length.
<?
$str = "It's been ten years since Dr. Hannibal \"The Cannibal\" Lecter
(Anthony Hopkins) escaped from a maximum-security
penitentiary - ten years in which he's roamed free,
indulging his very specialized tastes. But out
of sight is very definitely not out of mind - he
still haunts Clarice Starling (Julianne Moore),
now a special agent in the FBI.";
// returns a word-wrapped block of width 50 characters
/*
It's been ten years since Dr. Hannibal "The
Cannibal" Lecter (Anthony Hopkins) escaped from a
maximum-security penitentiary - ten years in which
he's roamed free, indulging his very specialized
tastes. But out of sight is very definitely not
out of mind - he still haunts Clarice Starling
(Julianne Moore), now a special agent in the FBI.
*/
echo wordwrap($str, 50);
?>
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