Question

I’m trying to validate and get an “interest rate” from user input.

I’m wanting to accept 1% -> 99%, with the ability for 0, 1 or 2 decimals. I also dont mind if they include a “%”.

i.e.

• 3.2
• 3.45%
• 44%
• 4.00%

The best I could find was

/([0-9]{1,2})%/

But thats as close as I could get… any help would be greatly appreciated.

Answer 1

<?php

$regex = '~^(\d{1,2})(\.(\d{1,2}))?\%?$~';

$shouldMatch = array(
    '3.2',
    '3.45%',
    '44%',
    '4.00%'
);

foreach( $shouldMatch as $interest ) {
    var_dump( preg_match( $regex, $interest ) );
}

Explanation on the regex: it must start (^) with one or two digits (\d{1,2}). Then, you can have one group that starts with a . (although, in the Netherlands, a comma would be used). Then, it must be followed by one or two digits. (.(\d{1,2})). That group is optional (?). Then, there’s an optional percent mark (%?) and the string should end there ($).

EDIT: You also might want to use a (faster?) non-regex alternative:

<?php

$shouldMatch = array(
    '3.2',
    '3.45%',
    '44%',
    '4.00%'
);

foreach( $shouldMatch as $interest ) {
    $interest = trim( $interest, '%' );

    var_dump( is_numeric( $interest ) && $interest < 100 );
}