Hi, I'm very new to regular expressions and need some help. I'm using HTML and PHP (with MySQL).

I have a couple of validation requirements I was wondering if someone could me in.

Validation #1

Validation rules:
 + be 5 to 8 characters in length
 + only contain number(s) or letter(s)
 + must start with a letter
 + must contain at least one letter and one number

Examples that will match:
  David4
  JO34B

Examples that will Not match:
  4Peter
  jac1
  fred_9

My failed attempt: ^(?=.{5-8})([[:alpha:]])+([0-9]{1})*




Validation #2

Validation rules:
 + be 4-10 characters in length
 + only contain number(s) or letter(s)
 + must contain at least one number and at least two letters

Examples that will match:
  victorzz77
  JO34B

Examples that will Not match:
  j361
  fred_9



Validation #3

Validation rules:
 + be 3-50 characters in length
 + only contain letter(s), hyphens(-) or space(s)

Examples that will match:
  The quick brown fox
  James-Brown

Examples that will Not match:
  9 feet below
  2a

My failed attempt: ^(?=.{3-50})(?=.*[a-zA-Z\q- \e])

Untested suggestions with some short explanations:

#1

^(?=.*[a-zA-Z])(?=.*\d)[a-zA-Z][a-zA-Z\d]{4,7}$

^                       // start of the string
(?=.*[a-zA-Z])          // must "see" 1 letter when looking ahead
(?=.*\d)                // must "see" 1 digit when looking ahead
[a-zA-Z]                // match 1 letter
[a-zA-Z\d]{4,7}         // match 4 to 7 letters or digits
$                       // end of the string

#2

^(?=(.*[a-zA-Z]){2})(?=.*\d)[a-zA-Z\d]{4,10}$

^                       // start of the string
(?=(.*[a-zA-Z]){2})     // must "see" 2 letters when looking ahead
(?=.*\d)                // must "see" 1 digit when looking ahead
[a-zA-Z\d]{4,10}        // match 4 to 10 letters or digits
$                       // end of the string

#3

^[a-zA-Z\s-]{3,50}$

^                       // start of the string
[a-zA-Z\s-]{3,50}       // match 3 to 50 letters. white space characters or hyphens
$                       // end of the string

Note that inside a character class, the hyphen does not need to be escaped if placed at the end, or start of the character class:

[a-c]   // matches 'a', 'b' or 'c'
[ac-]   // matches 'a', 'c' or '-'
[-ac]   // matches '-', 'a' or 'c'
[a\-c]  // matches 'a', '-' or 'c'

B.t.w., I forgot to compliment you with the way you asked your question: a detailed, and clearly communicated question with enough examples of what should, and shouldn't be matched. If only all questione here looked like that!

Key point for the first two validations: Think lookaheads like regex inside validators.

First One:
^(?=[a-zA-Z]+\d)[a-zA-Z0-9]{5,8}$
* Ensure that the variable contains a number which comes after at least one letter.

Second One:
^(?=[a-zA-Z]*\d)(?=(\d*[a-zA-Z]){2})[a-zA-Z0-9]{4,10}$
* Ensure that the variable contains a number which may have letter(s) before it.
* Ensure that the variable contains two letters (either side by side or separated by a number).

Third One:
^[-a-zA-Z ]{3,50}$

sempsteen:

...

Second One:
^(?=[a-zA-Z]*\d)(?=([a-zA-Z]\d*){2})[a-zA-Z0-9]{4,10}$
...

If the string starts with a number (the OP did not mention it should start with a letter!), your regex will fail.

Good point. I think this should do the job:

^(?=[a-zA-Z]*\d)(?=(\d*[a-zA-Z]){2})[a-zA-Z0-9]{4,10}$

Thanks

sempsteen:

Good point. I think this should do the job:

^(?=[a-zA-Z]*\d)(?=(\d*[a-zA-Z]){2})[a-zA-Z0-9]{4,10}$

Thanks

Yes!

; )

Fantastic, thank you so much!

 

 

np