Strip non alphanumeric characters from a string with php
July 27, 2006 by Emanuele Feronato
Filed Under Php •
Filed Under Php •
Very simple and useful code, but hard to find in the internet.
You may need it when you code an user authentication script and want to prevent the user to hack it with ascii injection.
I will use regular expressions because it is the quickest way, and we want to be quick (almost) everytime...
PHP:
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<?php
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$string_to_be_stripped = "Hi, I am a string and I need to be stripped...";
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?>
$new_string content will be: Hi I am a string and I need to be stripped without any coma or stop.
Enjoy.
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(6 votes, average: 4 out of 5) Loading ...17 Responses to “Strip non alphanumeric characters from a string with php”
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Actually, as written, the new string will be HiIamastringandIneedtobestripped. The second parameter in ereg_replace (in your example) is not a space, but “nothing”, so the alpha characters will be joined together in one long word.
also it’s really easy to do similar strips:
only keep letters:
$new_string = ereg_replace(”[^A-Za-z]“, “”, $string_to_be_stripped);
keep alphanumerics and dashes
$new_string = ereg_replace(”[^A-Za-z0-9-]“, “”, $string_to_be_stripped);
This page saved my behind this morning .. thanks to EVERYONE who contributed !
how about stripping only \n , \t characters only…?
This isn’t working for me for some reason. maybe preg_replace?
works great. thank you.
Thanks, I just improved that a bit, replacing spaces with a dash just before stripping non alphanum (or dashes).
This is useful to let users add valid “subdomains” strings.
I use this inside a class with my other “tools” :)
public static function stripText($text)
{
$text = strtolower(trim($text));
// replace all white space sections with a dash
$text = str_replace(’ ‘, ‘-’, $text);
// strip all non alphanum or -
$clean = ereg_replace(”[^A-Za-z0-9\-]“, “”, $text);
return $clean;
}
You’ve got to be kidding. This is the top google search for “php strip characters” and the post doesn’t even contain correct info?!?
Dude– that’s cool! Also on the hunt for a “html safe” function. Thinking of having custom blogs and incorporating limited HTML tags in the body (to include images, change fonts, etc) but would like to replace tags with hex encoded characters … anyway, sure I’ll find that somewhere — meanwhile; thanks for the regular expression. Sweet!
PS. re: Mark above — that’s a problem with Google, not this post! Last time I searched “Lithuanian Universities” I got up “Singapore”. Google! One day the revolution will come …
I use this to strip any character except alphanumeric chars and spaces.
$data=preg_replace(”/[^A-Za-z0-9\s\s+]/”,”,$data);
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Keep in mind that if you copy and paste code from this page into your code, it WILL NOT work because of slight formatting changes imposed by this page. For example, the simple double quote character is replaced by the fancy left & right slanted versions, which PHP doesn’t recognize as quotes. So paste and then check the details, then test and pay attention to any error messages.
Now, how do I count characters with diacritics such as áéíóú as valid letters (… and they’re expressed in UTF)
I tried
preg_replace(”/[^A-Za-z0-9\s\s+]/”,”,$data);
and I got
Parse error: syntax error, unexpected ‘[’
for Karl Groves:
to fix emanuele’s mistake you just need to add a space in the braclets, like this:
So that’s what a space looks like!
This saved my life.
My script that handles the creation of license files that are used to unlock a plugin I sell wasn’t stripping non ASCII’s, and whaddya know - non ASCII’s made the unlock-function within my plugin barf.
Thanks!