How to write Regular Expression for number,characters,alphanumeric

I am using Zend_Validate_Regex, I need开发者_运维知识库 the regular expression which has the following check,

1. 123456 - Accepted
2. 12345A - Accepted
3. A12345 - Accepted
4. ABCDEF - Accepted

Kindly help

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Use this regex: (?i)^[\da-f]+$

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If you are expecting an hexadecimal number, the regular expression is:

/[0-9A-F]*/

May be, you want to use also non capital letters:

/[0-9A-F]*/i

Or perhaps you want to use exactly 6 characters (numbers and letters):

/[0-9A-F]{6}/i