Whitespace in a database field is not removed by trim()

问题

I have some whitespace at the begining of a paragraph in a text field in MySQL.

Using trim($var_text_field) in PHP or TRIM(text_field) in MySQL statements does absolutely nothing. What could this whitespace be and how do I remove it by code?

If I go into the database and backspace it out, it saves properly. It's just not being removed via the trim() functions.

回答1:

function UberTrim($s) {
    $s = preg_replace('/\xA0/u', ' ', $s);  // strips UTF-8 NBSP: "\xC2\xA0"
    $s = trim($s);
    return $s;
}

The UTF-8 character encoding for a no-break space, Unicode (U+00A0), is the 2-byte sequence C2 A0. I tried to make use of the second parameter to trim() but that didn't do the trick. Example use:

assert("abc" === UberTrim("  \r\n  \xc2\xa0  abc  \t \xc2\xa0   "));

---

A MySQL replacement for TRIM(text_field) that also removes UTF no-break spaces, thanks to @RudolfRein's comment:

TRIM(REPLACE(text_field, '\xc2\xa0', ' '))

---

UTF-8 checklist:

(more checks here)

1. Make sure your PHP source code editor is in UTF-8 mode without BOM. Or set in the preferences.

2. Make sure your MySQL client is set for UTF-8 character encoding (more here and here), e.g.

   $pdo = new PDO('mysql:host=...;dbname=...;charset=utf8',$userid,$password); $pdo->exec("SET CHARACTER SET utf8");

3. Make sure your HTTP server is set for UTF-8, e.g. for Apache:

   AddDefaultCharset UTF-8

4. Make sure the browser expects UTF-8.

   header('Content-Type: text/html; charset=utf-8');

   or

   <meta http-equiv="Content-Type" content="text/html;charset=utf-8" />

回答2:

If the problem is with UTF-8 NBSP, another simple option is:

REPLACE(the_field, UNHEX('C2A0'), ' ')

回答3:

Try using the MySQL ORD() function on the text_field to check the character code of the left-most character. It can be a non-whitespace characters that appears like whitespace.

回答4:

The best solution is a combination of a few things mentioned to you already.

First run ORD() on the string in question. In my case I had to run a reverse first because my problem character was at the end of the string.

ORD(REVERSE([col name])) 

Once you discover the problematic char, run a

REPLACE([col_name], char([char_value_returned]), char(32))

Finally, call a proper

TRIM([col_name])

This will completely eradicate the problem character from all aspects of the string, and trim off the leading (in my case trailing) character.

回答5:

you have to detect these "whitespace" characters first. if it's some HTML entity, like   no trimming function would help, of course.

I'd suggest to print it out like this

echo urlenclde($row['field']);

and see what it says

Well as its A0 (or 160 decimal) non-breaking space character, you can convert it to ordinal space first:

<pre><?php
$str = urldecode("%A0")."bla";
var_dump(trim($str));
$str = str_replace(chr(160)," ",$str);
$str = trim($str);
var_dump($str);

and, ta-dam! -

string(4) " bla"
string(3) "bla"

回答6:

Try to check what character each "whitespace" is by writing the charactercode out - It might be a non-visible charactertype that isn't removed by trim. Trim only removes a few characters such as whitespace, tab, newline, CR and NUL but there exist other non-visible characters that might cause this problem.

回答7:

try

str_ireplace(array("\r", "\n", "\t"), $var_text_field

来源：https://stackoverflow.com/questions/5295936/whitespace-in-a-database-field-is-not-removed-by-trim