Remove Control Characters from PHP String

Remove control characters from PHP string

If you mean by control characters the first 32 ascii characters and \x7F (that includes the carriage return, etc!), then this will work:

preg_replace('/[\x00-\x1F\x7F]/', '', $input);

(Note the single quotes: with double quotes the use of \x00 causes a parse error, somehow.)

The line feed and carriage return (often written \r and \n) may be saved from removal like so:

preg_replace('/[\x00-\x09\x0B\x0C\x0E-\x1F\x7F]/', '', $input);

I must say that I think Bobby's answer is better, in the sense that [:cntrl:] better conveys what the code does than [\x00-\x1F\x7F].

WARNING: ereg_replace is deprecated in PHP >= 5.3.0 and removed in PHP >= 7.0.0!, please use preg_replace instead of ereg_replace:

preg_replace('/[[:cntrl:]]/', '', $input);

Remove control characters from string in PHP

You can use this replacement:

$result = preg_replace('~[^\P{Cc}\r\n]+~u', '', $str);

\p{Cc} is the unicode character class for control characters. \P{Cc} is the opposite (all that is not a control character).

[^\P{Cc}\r\n] is all that isn't \P{Cc}, \r and \n.

The u modifier ensures that the string and the pattern are read as utf8 strings.

If you want to preserve an other control character, for example the TAB, add it to the negated character class: [^\P{Cc}\r\n\t]

Remove all special characters from a string

This should do what you're looking for:

function clean($string) {
   $string = str_replace(' ', '-', $string); // Replaces all spaces with hyphens.

   return preg_replace('/[^A-Za-z0-9\-]/', '', $string); // Removes special chars.
}

Usage:

echo clean('a|"bc!@£de^&$f g');

Will output: abcdef-g

Edit:

Hey, just a quick question, how can I prevent multiple hyphens from being next to each other? and have them replaced with just 1?

function clean($string) {
   $string = str_replace(' ', '-', $string); // Replaces all spaces with hyphens.
   $string = preg_replace('/[^A-Za-z0-9\-]/', '', $string); // Removes special chars.

   return preg_replace('/-+/', '-', $string); // Replaces multiple hyphens with single one.
}

How to remove all non printable characters in a string?

7 bit ASCII?

If your Tardis just landed in 1963, and you just want the 7 bit printable ASCII chars, you can rip out everything from 0-31 and 127-255 with this:

$string = preg_replace('/[\x00-\x1F\x7F-\xFF]/', '', $string);

It matches anything in range 0-31, 127-255 and removes it.

8 bit extended ASCII?

You fell into a Hot Tub Time Machine, and you're back in the eighties.
If you've got some form of 8 bit ASCII, then you might want to keep the chars in range 128-255. An easy adjustment - just look for 0-31 and 127

$string = preg_replace('/[\x00-\x1F\x7F]/', '', $string);

UTF-8?

Ah, welcome back to the 21st century. If you have a UTF-8 encoded string, then the /u modifier can be used on the regex

$string = preg_replace('/[\x00-\x1F\x7F]/u', '', $string);

This just removes 0-31 and 127. This works in ASCII and UTF-8 because both share the same control set range (as noted by mgutt below). Strictly speaking, this would work without the /u modifier. But it makes life easier if you want to remove other chars...

If you're dealing with Unicode, there are potentially many non-printing elements, but let's consider a simple one: NO-BREAK SPACE (U+00A0)

In a UTF-8 string, this would be encoded as 0xC2A0. You could look for and remove that specific sequence, but with the /u modifier in place, you can simply add \xA0 to the character class:

$string = preg_replace('/[\x00-\x1F\x7F\xA0]/u', '', $string);

Addendum: What about str_replace?

preg_replace is pretty efficient, but if you're doing this operation a lot, you could build an array of chars you want to remove, and use str_replace as noted by mgutt below, e.g.

//build an array we can re-use across several operations
$badchar=array(
    // control characters
    chr(0), chr(1), chr(2), chr(3), chr(4), chr(5), chr(6), chr(7), chr(8), chr(9), chr(10),
    chr(11), chr(12), chr(13), chr(14), chr(15), chr(16), chr(17), chr(18), chr(19), chr(20),
    chr(21), chr(22), chr(23), chr(24), chr(25), chr(26), chr(27), chr(28), chr(29), chr(30),
    chr(31),
    // non-printing characters
    chr(127)
);

//replace the unwanted chars
$str2 = str_replace($badchar, '', $str);

Intuitively, this seems like it would be fast, but it's not always the case, you should definitely benchmark to see if it saves you anything. I did some benchmarks across a variety string lengths with random data, and this pattern emerged using php 7.0.12

     2 chars str_replace     5.3439ms preg_replace     2.9919ms preg_replace is 44.01% faster
     4 chars str_replace     6.0701ms preg_replace     1.4119ms preg_replace is 76.74% faster
     8 chars str_replace     5.8119ms preg_replace     2.0721ms preg_replace is 64.35% faster
    16 chars str_replace     6.0401ms preg_replace     2.1980ms preg_replace is 63.61% faster
    32 chars str_replace     6.0320ms preg_replace     2.6770ms preg_replace is 55.62% faster
    64 chars str_replace     7.4198ms preg_replace     4.4160ms preg_replace is 40.48% faster
   128 chars str_replace    12.7239ms preg_replace     7.5412ms preg_replace is 40.73% faster
   256 chars str_replace    19.8820ms preg_replace    17.1330ms preg_replace is 13.83% faster
   512 chars str_replace    34.3399ms preg_replace    34.0221ms preg_replace is  0.93% faster
  1024 chars str_replace    57.1141ms preg_replace    67.0300ms str_replace  is 14.79% faster
  2048 chars str_replace    94.7111ms preg_replace   123.3189ms str_replace  is 23.20% faster
  4096 chars str_replace   227.7029ms preg_replace   258.3771ms str_replace  is 11.87% faster
  8192 chars str_replace   506.3410ms preg_replace   555.6269ms str_replace  is  8.87% faster
 16384 chars str_replace  1116.8811ms preg_replace  1098.0589ms preg_replace is  1.69% faster
 32768 chars str_replace  2299.3128ms preg_replace  2222.8632ms preg_replace is  3.32% faster

The timings themselves are for 10000 iterations, but what's more interesting is the relative differences. Up to 512 chars, I was seeing preg_replace alway win. In the 1-8kb range, str_replace had a marginal edge.

I thought it was interesting result, so including it here. The important thing is not to take this result and use it to decide which method to use, but to benchmark against your own data and then decide.

Php remove special chracter from from last charcters of string

You can use rtrim() if the special characters you want to remove are known before-hand:

$string = rtrim($string, ',".');

The second parameter describes the list of characters that should be removed.

Demo

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If the special characters aren't known, then you could use a regex solution. The below preg_replace() statement will remove any character that's not a word character ([a-zA-Z0-9_], or a hyphen (-) or a single-quote ('):

preg_replace('/[^\w\-\']$/', '', $str);  

Explanation:

• [^\w-\'] - match a single character not present in the list
  
  • \w - any word character [a-zA-Z0-9_]
  • \- - the literal character -
  • \' - the literal character '
• $ - "end of line" anchor - used to assert position at end of the string

PHP replace special characters from a string

Add those characters you want to keep to preg, also add Upper cases if neededç I edited your code:

function clean($string) {
    $string = str_replace(' ', ' ', $string);
    $string = preg_replace('/[^A-Za-z0-9\-ığşçöüÖÇŞİıĞ]/', ' ', $string);

    return preg_replace('/-+/', '-', $string);
}

Test:

$str='Merhaba=Türkiye 12345 çok çalış another one ! *, !@_';
var_dump(clean($str));
//Output: string(57) "Merhaba Türkiye 12345 çok çalış another one   "

Removing special Characters from string

try to replace the regular expectation
change

preg_replace('/[^A-Za-z0-9\-]/', '', $string);

with

preg_replace("/[^A-Za-z0-9\-\']/", '', $string);  // escape apostraphe

or

you can str_replace It is quicker and easier than preg_replace() Because it does not use regular expressions.

$text = str_replace("'", '', $string);

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