Regex for two latitudes and longitudes not working

Question

I am using some data which gives paths for google maps either as a path or a set of two latitudes and longitudes. I have stored both values as a BLOB in a mySql database, but I need to detect the values which are not paths when they come out in the result. In an attempt to do this, I have saved them in the BLOB in the following format:

array(lat,lng+lat,lng)

I am using preg_match to find these results, but i havent managed to get any to work. Here are the regex codes I have tried:

^[a]{1}[r]{2}[a]{1}[y]{1}[\(]{1}[1-9\.\,\+]{1*}[\)]{1}^

^[a]{1}[r]{2}[a]{1}[y]{1}[\(]{1}(\-?\d+(\.\d+)?),(\-?\d+(\.\d+)?)\+(\-?\d+(\.\d+)?),(\-?\d+(\.\d+)?)[\)]{1}^

Regex confuses me sometimes (as it is doing now). Can anyone help me out?

Edit:

The lat can be 2 digits followed by a decimal point and 8 more digits and the lng can be 3 digits can be 3 digits follwed by a decimal point and 8 more digits. Both can be positive or negative.

Here are some example lat lngs:

51.51160000,-0.12766000

-53.36442000,132.27519000

51.50628000,0.12699000

-51.50628000,-0.12699000

So a full match would look like:

array(51.51160000,-0.12766000+-53.36442000,132.27519000)

Further Edit

I am using the preg_match() php function to match the regex.

Answer 1

This is the regex I made:

array\((-*\d+\.\d+),(-*\d+\.\d+)\+(-*\d+\.\d+),(-*\d+\.\d+)\)

This also breaks the four numbers into groups so you can get the individual numbers.

You will note the repeated pattern of

(-*\d+\.\d+)

Explanation:

-* means 0 or more matches of the - sign ( so - sign is optional)
\d+ means 1 or more matches of a number
\. means a literal period (decimal)
\d+ means 1 or more matches of a number

The whole thing is wrapped in brackets to make it a captured group.

Answer 2

Here are some pointers for writing regex:

If you have a single possibility for a character, for example, the a in array, you can indeed write it as [a]; however, you can also write it as just a.

If you are looking to match exactly one of something, you can indeed write it as a{1}, however, you can also write it as just a.

Applying this lots, your example of ^[a]{1}[r]{2}[a]{1}[y]{1}[\(]{1}[1-9\.\,\+]{1*}[\)]{1}^ reduces to ^array\([1-9\.\,\+]{1*}\)^ - that's certainly an improvement!

Next, numbers may also include 0's, as well as 1-9. In fact, \d - any digit - is usually used instead of 1-9.

You are using ^ as the delimiter - usually that is /; I didn't recognize it at first. I'm not sure what you can use for the delimiter, so, just in case, I'll change it to the usual /.This makes the above regex /array\([\d\.\,\+]{1*}\)/.

To match one or more of a character or character set, use +, rather than {1*}. This makes your query /array\([\d\.\,\+]+\)/

Then, to collect the resulting numbers (assuming you want only the part between the brackets, put it in (non-escaped) brackets, thus: /array\(([\d\.\,\+]+)\)/ - you would then need to split them, first by +, then by ,. Alternatively, if there are exactly two lat,lng pairs, you might want: /array\(([\d\.]+),([\d\.]+)\+([\d\.]+),([\d\.]+)\)/ - this will return 4 values, one for each number; the additional stuff (+, ,) will already be removed, because it is not in (unescaped) brackets ().

Edit: If you want negative lats and longs (and why wouldn't you?) you will need \-? (a "literal -", rather than part of a range) in the appropriate places; the ? makes it optional (i.e. 0 or 1 dashes). For example, /array\((\-?[\d\.]+),(\-?[\d\.]+)\+(\-?[\d\.]+),(\-?[\d\.]+)\)/

You might also want to check out http://regexpal.com - you can put in a regex and a set of strings, and it will highlight what matches/doesn't match. You will need to exclude the delimiter / or ^.

Note that this is a little fast and loose; it would also match array(5,0+0,1...........). You can nail it down a little more, for example, by using (\-?\d*\.\d+)\) instead of (\-?[\d\.]+)\) for the numbers; that will match (0 or 1 literal -) followed by (0 or more digits) followed by (exactly one literal dot) followed by (1 or more digits).