php Validate latitude/longitude strings in decimal format

Question

Alright I have what I would call a massive list of longitude and latitude coordinates. That said I also have a handful of sources I pull these coordinates in from. Some of them come from get/post methods which can cause potential security holes in my site/service. So I am trying to figure out how to validate longitude and latitude via PHP. I was thinking something regex via preg_match. But I could be wrong, maybe there's an easier way someone would like to suggest. I've tried my own concepts, and I have tried various internet brew concepts of trying to find a regex pattern that will validate these for me via preg_match (or similar again if you got a better suggestion I am all ears).

My Last failed attempt prior to finally caving in and coming here was..

preg_match('^(\-?\d+(\.\d+)?),\s*(\-?\d+(\.\d+)?)$', $geoResults['latitude']))

which yields " preg_match() [function.preg-match]: No ending delimiter '^' found " as my error. Last couple attempts I have tried yielded that error so I have no idea what it is or means.

Piker

This would also match 400.00,-700 as being a valid lat/lng. – Girosol

Answer 1

Add forward slashes to the beginning and end of the match sequence to make it valid regex syntax:

preg_match('/^(\-?\d+(\.\d+)?),\s*(\-?\d+(\.\d+)?)$/', $geoResults['latitude']);

For your question on whether to use regular expressions (regex) or not, in this case using regex (PCRE preg_match()) is the best way to secure your site. When matching variable complex string arrangements, regex is the way to go. It's common for developers to turn to regex for matching a static string such as 'abc'. This is when strpos() or str_replace() are better choices.

Nearsighted

this gets me on the right track however I am using it in an if statement.. if this match is invalid should i be using !preg_match or just preg_match? – Piker

@Piker preg_match returns 1 (true) if a match is found, otherwise 0. If you want to check if it hasn't found a match, use !preg_match() – Nearsighted

@ChrisBornhoft is not working with -74.052638804=3612 – Repay

@OscarDavid if you're using = as a delimiter (also 3612 is not a valid lat/lng), you'll need to alter the expression to reflect that. – Nearsighted

It's not delimiter... It's a wrong longitude but the expression didn't detect the mistake – Repay

Answer 2

It's a bit old question, but anyway I post my solution here:

preg_match('/^[-]?(([0-8]?[0-9])\.(\d+))|(90(\.0+)?);[-]?((((1[0-7][0-9])|([0-9]?[0-9]))\.(\d+))|180(\.0+)?)$/', $geoResults['latlng']);

I assumed here that u split lat. from lng. by semicolon. If u want to check only lat. or only lng. here are regexp's;

Rgx for lat.:

/^[-]?(([0-8]?[0-9])\.(\d+))|(90(\.0+)?)$/

Rgx for lng.:

/^[-]?((((1[0-7][0-9])|([0-9]?[0-9]))\.(\d+))|180(\.0+)?)$/

Here is an improved online demo: https://regex101.com/r/bV5fA1/1

Oceanography

Why the limit at 80 and 179? – Grantham

I've edited my posted and changed the limits to 89.(9) and 179.(9). Why? Becouse of point 179.(9) and -179.(9) are pretty the same and it allows to make rgx easier. – Oceanography

Better but not suficient, lat 90 and long 180 are perfectly valid. – Grantham

Edited once again. Now lat 90 and lng 180 will be valid ;) Thanks for suggestions. – Oceanography

OK, +1 but you should escape the dot in (.0+). – Grantham

Done. Thank you for appreciation and your help to finally create a valid answer. – Oceanography

[0-8]? should be replaced with [1-9]? to make values like 05.12345 invalid. Anyway, thank you for your regexp! PS: The same with [0-9]? for longitude. – Promptitude

I tried to test on 0.000000;0.000000, yes I know they are still valid and point to a certain location but in my case that's never gonna happen and it's a bit of an overkill but other then that your solution is awesome! – Besse

Answer 3

Why not use modern and unit tested Assertion library for that?

Example Value Object class:

<?php
namespace MyApp\ValueObject;

use Assert\Assertion;

class Location
{
    private $lat;
    private $lon;

    public function __construct($lat, $lon)
    {
        Assertion::greaterOrEqualThan($lat, -90.0);
        Assertion::lessOrEqualThan($lat, 90.0);
        Assertion::greaterOrEqualThan($lon, -180.0);
        Assertion::lessOrEqualThan($lon, 180.0);

        $this->lat = $lat;
        $this->lon = $lon;
    }

    public function latitude()
    {
        return $this->lat;
    }

    public function longitude()
    {
        return $this->lon;
    }

    public function __toString()
    {
        return $this->lat . ' ' . $this->lon;
    }

Usage:

$location = new \MyApp\ValueObject\Location(24.7, -20.4059);

echo $location->latitude() , ' ' , $location->longitude();

// or simply

echo $location;

PHP8.2 update:

final readonly class Location implements \Stringable
{
    public function __construct(
        private float $lat,
        private float $lon,
    ) {
        Assertion::greaterOrEqualThan($this->lat, -90.0);
        Assertion::lessOrEqualThan($this->lat, 90.0);
        Assertion::greaterOrEqualThan($this->lon, -180.0);
        Assertion::lessOrEqualThan($this->lon, 180.0);
    }

    public function latitude(): float
    {
        return $this->lat;
    }

    public function longitude(): float
    {
        return $this->lon;
    }

    public function __toString(): string
    {
        return $this->lat . ' ' . $this->lon;
    }
}

Slavey

Answer 4

I want to validate latitude and longitude, too, and have this result:

-90.0000 - 90.0000

^-?([0-9]|[1-8][0-9]|90)\.{1}\d{4}$

-180.0000 - 180.0000

^-?([0-9]|[1-9][0-9]|1[0-7][0-9]|180)\.{1}\d{4}$

I have tested here with pcre.

Alectryomancy

You should post this as 1 regex to fetch both lat and long from the same line. Also, [0-9]|[1-9][0-9] can be simplified as [1-9]?[0-9]. – Topliffe

Answer 5

regex

/([0-9.-]+).+?([0-9.-]+)/

Ambience

Please, add explanation for your answer – Candor

Answer 6

Function to validate Latitude

function validateLatitude($lat) {


    $lat_array = explode( '.' , $lat );

    if( sizeof($lat_array) !=2 ){
        return '_n_';
    }

    if ( ! ( is_numeric($lat_array[0]) && $lat_array[0]==round($lat_array[0], 0) && is_numeric($lat_array[1]) && $lat_array[1]==round($lat_array[1], 0)  ) ){
        return '_n_';
    }

    if( $lat >= -90 && $lat <= 90 ){
        return '_s_';
    }
    else {
        return '_n_';
    }

}

Function to validate Longitude

function validateLongitude($long) {

    $long_array = explode( '.' , $long );

    if( sizeof($long_array) !=2 ){
        return '_n_';
    }

    if (!( is_numeric($long_array[0]) && $long_array[0]==round($long_array[0], 0) && is_numeric($long_array[1]) && $long_array[1]==round($long_array[1], 0)  ) ){
        return '_n_';
    }

    if( $long >= -180 && $long <= 180 ){
        return '_s_';
    }
    else {
        return '_n_';
    }

}

Oswell

Answer 7

It's real work unicum solution in net " -90.0000 - 90.0000

^-?([0-9]|[1-8][0-9]|90)\.{1}\d{4}$

-180.0000 - 180.0000

^-?([0-9]|[1-9][0-9]|1[0-7][0-9]|180)\.{1}\d{4}$
"

For &lat=90.000000 &lon=180.000000 :

"/^-?([0-9]|[1-8][0-9]|90)\.{1}\d{1,6}$/"

"/^-?([1]?[1-7][1-9]|[1]?[1-8][0]|[1-9]?[0-9])\.{1}\d{1,6}/"

Vanna

Answer 8

These didn't seem very accurate being that:

latitude is between -90 and 90

longitude is between -180 and 90

and

\d in regex matches more than [0-9]

Also a whole library just for some regex didn't seem logical...

So I built and tested:

//Latitude
if(preg_match('/^-?(90|[1-8][0-9][.][0-9]{1,20}|[0-9][.][0-9]{1,20})$/', '89.33333')) {
                            echo "<br>a match<br>"; 
} //will pass ->89.33333


//Longitude
if(preg_match('/^-?(180|1[1-7][0-9][.][0-9]{1,20}|[1-9][0-9][.][0-9]{1,20}|[0-9][.][0-9]{1,20})$/', '180.33333')) {
                            echo "<br>b match<br>"; 
} // will fail anything over 180 ->180.33333

Overuse