[charachterclass help] Matching certain characters of a string?

Beginners - Learning PHP
#1

I have a string suppose “ABCDEF>(#*W” (could be any string)

I want a function character class, such that it returns a false value if any other character then “A-Z or a-z or 0-9 or @ or $ or [ or ] or ( or ) or . or _” exists in the string.

More explanation:
$string=“A.BC_@$09” //this should return true value, no invalid characters in it.
$string=“ABC DEF” //this should return false value (because it has space)
$string=“ABC_><” //this should return false value (because > and < characters are invalid)
$string=“ABCDEF” //this should return true value, no invalid characters in it.

Actually allowed characters are:

0-9 a-z A-Z @ $ [ ] ( ) . _

I am really weak in character classes, would be grateful if someone can get me through this.

#2

Just curious why do you need to return true when you can just remove the characters?

#3

Just to answer your question, see the function ctype_alnum()

#4

because I need to return error to the user if he uses invalid symbols

#5

Ok I have used if condition.

Thanks.

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