I'm looking for a php function that will take an input string and return a sanitized version of it by stripping away all special characters leaving only alpha-numeric.
I need a second function that does the same but only returns alphabetic characters A-Z.
Any help much appreciated.
Warning: Note that English is not restricted to just A-Z.
Try this to remove everything except a-z, A-Z and 0-9:
$result = preg_replace("/[^a-zA-Z0-9]+/", "", $s);
If your definition of alphanumeric includes letters in foreign languages and obsolete scripts then you will need to use the Unicode character classes.
Try this to leave only A-Z:
$result = preg_replace("/[^A-Z]+/", "", $s);
The reason for the warning is that words like résumé contains the letter é that won't be matched by this. If you want to match a specific list of letters adjust the regular expression to include those letters. If you want to match all letters, use the appropriate character classes as mentioned in the comments.
[\p{Alphabetic}\p{Numeric}]. I forget the PCRE alphabetic property, but you can approximate it with [\pL\pM\pN].
[A-Z] is always wrong, sometimes .
i but I have only ever has to worry about an English demographic .. I forget many people have to think about other languages. BTW I just noticed you are the highest rep'd user who has never asked 1 question. Even Jon Skeet has asked questions before!
try this to keep accentuated characters:
$result = preg_replace("/[^A-zÀ-ú0-9]+/", "", $s);
Rather than preg_replace, you could always use PHP's filter functions using the filter_var() function with FILTER_SANITIZE_STRING.
FILTER_SANITIZE_STRING? To my knowledge, the closest that can be archieved this way is with FILTER_SANITIZE_STRING, FILTER_FLAG_STRIP_LOW | FILTER_FLAG_STRIP_HIGH, but that won't leave just letters and numbers but also dots, slashes, percents and that all.
If You want to keep only alphanumeric with language-specific accents I would rather use:
$clean_string = preg_replace("/[^\w\s+$]/u", "", $string);
This will do the job and keep special characters like: ą, ó, ę, ö, ñ.
unichars '\p{Latin}' '\p{Alphabetic}' '[^A-Za-z]' | wc -l== 1192 code points that are Latin alphabetics but which are not A-Z. It is commonly held myth that ASCII is enough for English. It’s not, and that’s why writing A-Z has a code smell to it.