Você procurou por: alphanumeric (Coreano - Espanhol)

returns an associative array containing information about a user referenced by an alphanumeric username, passed in the username parameter.
este debe ser el mismo que el parámetro username usado en la llamada a la función y por lo tanto es redundante.

session.name specifies the name of the session which is used as cookie name. it should only contain alphanumeric characters. defaults to phpsessid.
les daremos un pequeño repaso.

참고: if a value in the ini file contains any non-alphanumeric characters it needs to be enclosed in double-quotes (").
nota:

an opening square bracket introduces a character class, ter- minated by a closing square bracket. a closing square bracket on its own is not special. if a closing square bracket is required as a member of the class, it should be the first data character in the class (after an initial cir- cumflex, if present) or escaped with a backslash. a character class matches a single character in the subject; the character must be in the set of characters defined by the class, unless the first character in the class is a cir- cumflex, in which case the subject character must not be in the set defined by the class. if a circumflex is actually required as a member of the class, ensure it is not the first character, or escape it with a backslash. for example, the character class [aeiou] matches any lower case vowel, while [^aeiou] matches any character that is not a lower case vowel. note that a circumflex is just a con- venient notation for specifying the characters which are in the class by enumerating those that are not. it is not an assertion: it still consumes a character from the subject string, and fails if the current pointer is at the end of the string. when caseless matching is set, any letters in a class represent both their upper case and lower case versions, so for example, a caseless [aeiou] matches "a" as well as "a", and a caseless [^aeiou] does not match "a", whereas a case- ful version would. the newline character is never treated in any special way in character classes, whatever the setting of the pcre_dotall or pcre_multiline options is. a class such as [^a] will always match a newline. the minus (hyphen) character can be used to specify a range of characters in a character class. for example, [d-m] matches any letter between d and m, inclusive. if a minus character is required in a class, it must be escaped with a backslash or appear in a position where it cannot be inter- preted as indicating a range, typically as the first or last character in the class. it is not possible to have the literal character "]" as the end character of a range. a pattern such as [w-]46] is interpreted as a class of two characters ("w" and "-") fol- lowed by a literal string "46]", so it would match "w46]" or "-46]". however, if the "]" is escaped with a backslash it is interpreted as the end of range, so [w-\]46] is inter- preted as a single class containing a range followed by two separate characters. the octal or hexadecimal representation of "]" can also be used to end a range. ranges operate in ascii collating sequence. they can also be used for characters specified numerically, for example [\000-\037]. if a range that includes letters is used when caseless matching is set, it matches the letters in either case. for example, [w-c] is equivalent to [][\^_`wxyzabc], matched caselessly, and if character tables for the "fr" locale are in use, [\xc8-\xcb] matches accented e characters in both cases. the character types \d, \d, \s, \s, \w, and \w may also appear in a character class, and add the characters that they match to the class. for example, [\dabcdef] matches any hexadecimal digit. a circumflex can conveniently be used with the upper case character types to specify a more res- tricted set of characters than the matching lower case type. for example, the class [^\w_] matches any letter or digit, but not underscore. all non-alphanumeric characters other than\, -, ^ (at the start) and the terminating] are non-special in character classes, but it does no harm if they are escaped.
subpatrones condicionales es posible hacer que el casamiento procese un subpatrón condicionalmente o elegir entre dos subpatrones alternativos, dependiendo del resultado de una sentencia o si un subpatrón capturado previamente casó o no.