Regular Expression for simple password

[kkobashi]

Can someone help me with coming up with a regular expression that would allow a password to have letters (A-Z, a-z) and numbers (0-9) in it?

Would this work?

ereg("^{[a-zA-Z0-9]*",} $password)

meaning:

First character is a letter or number followed by zero or more letters/numbers.

Thanks!

[mrhappiness]

• means zero or more occurrences
• means at least one occurence

[Kudose]

<?php
//this works

if(eregi("^([A-Za-z]{1})+([A-Za-z0-9])+$", "aa12a3")){ echo "True "; } else { echo 'False '; }
if(eregi("^([A-Za-z]{1})+([A-Za-z0-9])+$", "a123s2")){ echo "True "; } else { echo 'False '; }
if(eregi("^([A-Za-z]{1})+([A-Za-z0-9])+$", "1a2323")){ echo "True "; } else { echo 'False '; }
if(eregi("^([A-Za-z]{1})+([A-Za-z0-9])+$", "aaaaaa")){ echo "True "; } else { echo 'False '; }
if(eregi("^([A-Za-z]{1})+([A-Za-z0-9])+$", "111111")){ echo "True "; } else { echo 'False '; }
if(eregi("^([A-Za-z]{1})+([A-Za-z0-9])+$", "a1223c")){ echo "True "; } else { echo 'False '; }
?>

Output

True True False True False True 

[kkobashi]

Originally posted by mrhappiness
* means zero or more occurrences
+ means at least one occurence

So would this work?

ereg("^{[a-zA-Z0-9]+",} $password)

Interpretation:
The first character can be a letter or number followed by one or more letters/numbers. This would force at least a 2 character password.

ereg("^{[a-zA-Z0-9]*",} $password)

Interpretation:
The first character can be a letter or number followed by zero or more letters/numbers. This would force at least a 1 character password.

[mrhappiness]

interpretation is wrong

^[a-zA-Z0-9]+ first character has to be number or letter followed by numbers and letters or nothing => at leass 1 character passwords

^[a-zA-Z0-9]* first character has to be number or letter or nothing=> at least 0 character passwords

[kkobashi]

Thanks mrhappiness.

^[a-zA-Z0-9]+ seems reasonable since it requires at least 1 character.

Now what if I desire to have a password of at least 4 letters/numbers and no more than 10 letters/numbers?

Would it be:
^{[a-zA-Z0-9]{4,10}}

Php:

$this->minpasswordlength = 4;
$this->maxpasswordlength = 10;
if (!ereg("^{[a-zA-Z0-9]{$this->minpasswordlength,$this->maxpasswordlength}",} $_POST["txtPassword"])
{
echo "Passwords can only contain letters and numbers and must be a minimum of $this->minpasswordlength characters and maximum of $this->maxpasswordlength characters";
return(FALSE);
}

[mrhappiness]

Originally posted by kkobashi
Would it be

Would you try 😉