[php] Remove excess whitespace from within a string

I receive a string from a database query, then I remove all HTML tags, carriage returns and newlines before I put it in a CSV file. Only thing is, I can't find a way to remove the excess white space from between the strings.

What would be the best way to remove the inner whitespace characters?

If you want to replace only multiple spaces in a string, for Example: "this string have lots of space . " And you expect the answer to be "this string have lots of space", you can use the following solution:

$strng = "this string                        have lots of                        space  .   ";

$strng = trim(preg_replace('/\s+/',' ', $strng));

echo $strng;

$str = "I      am a PHP   Developer";
$str_length = strlen($str);
$str_arr = str_split($str);
for ($i = 0; $i < $str_length; $i++) {
   if (isset($str_arr[$i + 1])  && $str_arr[$i] == ' ' && $str_arr[$i] == $str_arr[$i + 1]) {
       unset($str_arr[$i]);
   } 
   else {
     continue;
   }
}
echo implode("", $str_arr);

$str = str_replace(' ','',$str);

Or, replace with underscore, & nbsp; etc etc.

There are security flaws to using preg_replace(), if you get the payload from user input [or other untrusted sources]. PHP executes the regular expression with eval(). If the incoming string isn't properly sanitized, your application risks being subjected to code injection.

In my own application, instead of bothering sanitizing the input (and as I only deal with short strings), I instead made a slightly more processor intensive function, though which is secure, since it doesn't eval() anything.

function secureRip(string $str): string { /* Rips all whitespace securely. */
  $arr = str_split($str, 1);
  $retStr = '';
  foreach ($arr as $char) {
    $retStr .= trim($char);
  }
  return $retStr;
}

$str = preg_replace('/[\s]+/', ' ', $str);

You can use:

$str = trim(str_replace("  ", " ", $str));

This removes extra whitespaces from both sides of string and converts two spaces to one within the string. Note that this won't convert three or more spaces in a row to one! Another way I can suggest is using implode and explode that is safer but totally not optimum!

$str = implode(" ", array_filter(explode(" ", $str)));

My suggestion is using a native for loop or using regex to do this kind of job.

$str = trim(preg_replace('/\s+/',' ', $str));

The above line of code will remove extra spaces, as well as leading and trailing spaces.

none of other examples worked for me, so I've used this one:

trim(preg_replace('/[\t\n\r\s]+/', ' ', $text_to_clean_up))

this replaces all tabs, new lines, double spaces etc to simple 1 space.

To expand on Sandip’s answer, I had a bunch of strings showing up in the logs that were mis-coded in bit.ly. They meant to code just the URL but put a twitter handle and some other stuff after a space. It looked like this

? productID =26%20via%20@LFS

Normally, that would‘t be a problem, but I’m getting a lot of SQL injection attempts, so I redirect anything that isn’t a valid ID to a 404. I used the preg_replace method to make the invalid productID string into a valid productID.

$productID=preg_replace('/[\s]+.*/','',$productID);

I look for a space in the URL and then remove everything after it.

I wrote recently a simple function which removes excess white space from string without regular expression implode(' ', array_filter(explode(' ', $str))).