$data contains tabs, leading spaces and multiple spaces. I wish to replace all tabs with a space. Multiple spaces with one single space, and remove leading spaces.
In fact somthing that would turn this input data:
[ asdf asdf asdf asdf ]
Into output data:
[asdf asdf asdf asdf]
How do I do this?
Trim, replace tabs and extra spaces with single spaces:
$data = preg_replace('/[ ]{2,}|[\t]/', ' ', trim($data));
tab space tab space tab space. Did you test this?
$data = trim(preg_replace('/\s+/g', '', $data));
$data = trim($data);
That gets rid of your leading (and trailing) spaces.
$pattern = '/\s+/';
$data = preg_replace($pattern, ' ', $data);
That turns any collection of one or more spaces into just one space.
$data = str_replace("\t", " ", $data);
That gets rid of your tabs.
\s you don't need \tAssuming the square brackets aren't part of the string and you're just using them for illustrative purposes, then:
$new_string = trim(preg_replace('!\s+!', ' ', $old_string));
You might be able to do that with a single regex but it'll be a fairly complicated regex. The above is much more straightforward.
Note: I'm also assuming you don't want to replace "AB\t\tCD" (\t is a tab) with "AB CD".
preg_replace is "complicated".This answer takes the question completely literally: it is only concerned with spaces and tabs. Granted, the OP probably also wants to include other kinds of whitespace in what gets trimmed/compressed, but let's pretend he wants to preserve embedded CR and/or LF.
First, let's set up some constants. This will allow for both ease of understanding and maintainability, should modifications become necessary. I put in some extra spaces so that you can compare the similarities and differences more easily.
define( 'S', '[ \t]+' ); # Stuff you want to compress; in this case ONLY spaces/tabs
define( 'L', '/\A'.S.'/' ); # stuff on the Left edge will be trimmed
define( 'M', '/'.S.'/' ); # stuff in the Middle will be compressed
define( 'R', '/'.S.'\Z/' ); # stuff on the Right edge will be trimmed
define( 'T', ' ' ); # what we want the stuff compressed To
We are using \A and \Z escape characters to specify the beginning and end of the subject, instead of the typical ^ and $ which are line-oriented meta-characters. This is not so much because they are needed in this instance as much as "defensive" programming, should the value of S change to make them needed in the future.
Now for the secret sauce: we are going to take advantage of some special semantics of preg_replace, namely (emphasis added)
If there are fewer elements in the replacement array than in the pattern array, any extra patterns will be replaced by an empty string.
function trim_press( $data ){
return preg_replace( [ M, L, R ], [ T ], $data );
}
So instead of a pattern string and replacement string, we are using a pattern array and replacement array, which results in the extra patterns L and R being trimmed.
In case you need to remove too.
$data = trim(preg_replace('/\s+|nbsp;/g', '', $data));
After much frustration I found this to be the best solution, as it also removes non breaking spaces which can be two characters long:
$data = html_entity_decode(str_replace(' ',' ',htmlentities($data)));
$data = trim(preg_replace('/\h/', ' ', $data)); // replaces more space character types than \s
See billynoah
Just use this regex
$str = trim(preg_replace('/\s\s+/', ' ', $str));
it will replace all tabs and spaces by one space,
here sign + in regex means one or more times,
pattern means, that wherever there are two or more spaces, replace it by one space
