Question

So I know it would be easier to just use the php is_numeric function, but what i’m trying to do is create a regular expression, mostly for learning regex, to test test scores. The range can be 0-100, but can have 2 decimal places. This is what I have so far and its not working.

  if (preg_match("^([0-9]){2,3})(.[0-9]{2})?$([0-9]{1})?$", $quiz1))
    {
        echo "match";
    }
    else {
        $error = true;
    }

If I’m thinking correctly the literal meaning:

start of string find characters 0-9, for two places.
optional end of string decimal and find characters 0-9, for two places.
optional end of string find characters 0-9, for 1 place.

Answer 1

Why not something like this?

 /^(?:100|\d{1,2})(?:\.\d{1,2})?$/

• ^ – beginning of string
• (?:100|\d{1,2}) – non-capturing group, 100 or 0-99
• (?:.\d{1,2})? – optional non-capturing group (.# or .##)
• $ – end of string

Results:

php > $tests = array(0, 5, 10, 50, 100, 99.5, 75.43, 75.436, 101);

php > foreach ($tests as $test) { print $test . ” – ” . preg_match(“/^(?:100|\d{1,2})(?:\.\d{1,2})?$/”, $test) . “\n”; }

0 – 1

5 – 1

10 – 1

50 – 1

100 – 1

99.5 – 1

75.43 – 1

75.436 – 0

101 – 0

75F43 – 0

Yours doesn’t work even when I add the slashes and remove the extra ).

php > foreach ($tests as $test) { print $test . ” – ” .
preg_match(“/^([0-9]{2,3})(.[0-9]{2})?$([0-9]{1})?$/”, $test) . “\n”; }
0 – 0

5 – 0

10 – 1

50 – 1

100 – 1

99.5 – 0

75.43 – 1

75.436 – 0

101 – 1

75F43 – 1