how to validate numeric strings in PHP

Question

I'm looking for a method that would allow me to check for valid IDs in my system.

They're by definition:

positive, not 0,
a whole number, but might be bigger than integer size
come as either string or number

I'd like to know what you think is the most elegant way of validating this. Candidates that fail are:

is_int(), because it's valid for negative numbers, AND because of the integer size limit
is_numeric(), because it'd valid for float, or, say, having an exponential part like this +0123.45e6
ctype_digit() with casting the input to string, because this would be valid: "0000"

I've so far settled with this:

preg_match('/^[1-9][0-9]*$/',(string)$id);

Can anyone come up with an alternative?

possible duplicate of stackoverflow.com/questions/1969464/… — Fahim Parkar
– Fahim Parkar, Commented Jan 16, 2012 at 11:06
not quite: the real kicker is the "bigger than int" while still a whole number. It could apply to the person asking in the other thread, though, if his tables get real big. — Matthias
– Matthias, Commented Jan 16, 2012 at 12:22
Note: I'm aware that creating a function, combining various methods, is a possibility (which I'm using in practice, I don't expose the regexp every time), I'm wondering if PHP is offering me something more elegant. — Matthias
– Matthias, Commented Jan 16, 2012 at 12:24

Elzo Valugi · Accepted Answer · 2012-01-16 11:06:21Z

3

Try filter_var functions with FILTER_VALIDATE_INT. For valid integers you can specify ranges.Probably has the same limitaton with the size limit, but for that you'll have to build a custom function that serve exactly your requirements.

answered Jan 16, 2012 at 11:06

Elzo Valugi

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4 Comments

Matthias Over a year ago

I guess I could wrap it in filter var, like:

Matthias Over a year ago

I guess I could wrap it in filter_var, like: filter_var((string) $id, FILTER_VALIDATE_REGEXP, array('options' => array('regexp' => '/^[1-9][0-9]*$/')) ); probably a good idea when that's a project-wide validation approach (which it isn't right now)

Elzo Valugi Over a year ago

my real question is why are you using id with INT over the INT limits? this will turn against you at some point. Use another combination of key if you need more keys

Matthias Over a year ago

The definition of the id is outside of my control. That said, I'm not "using id with INT" over its limits; it's not INT at all, just a whole number as a string. I wildly guess it has something to do with id pools and distributed servers and stuff. Mainly with stuff, though.

Community · Accepted Answer · 2023-11-17 20:29:45Z

0

you could use

function vaild_id($passed_value=-1)
{
    if((is_int($passed_value)) && ($passed_value > 0)) return true;
    else return false; 
}

this will also allow you to add other rules to it if you need to

notes: is_int [and php] have a limit on the total size of integers allowed depending on if your working on 32 or 64bit so do that that into account php.net comment on is_int about system bit environment

edited Nov 17, 2023 at 20:29

CommunityBot

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answered Jan 16, 2012 at 11:08

Madpeter

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3 Comments

Konrad Dzwinel Over a year ago

And what about integer size limit: is_int( 2147483648 );// false?

Madpeter Over a year ago

added note about is_int size limit

Matthias Over a year ago

yes, it's of no use if it limits me to the size of int, be that 32 or 64 bit environments

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