Regex to extract weather forecast, and add to an array - php

Question

I've bought RegexBuddy, given it a try and unless I am matching on something static, and simple - I just can't get regex!
What I am trying to do is from the following line of text; I would like to extract tidal information into an associative array.
High Tide: 2.0m on Mon at 08.54pm and 2.4m on Tue at 09.18am
And end up with the following array:
[0] =
'Day' => 'Mon',
'Time' => '8.54pm',
'Height' => '2.0m',
'Tide' => 'High'
[1] =
'Day' => 'Tue',
'Time' => '09.18am',
'Height' => '2.4m',
'Tide' => 'High'
The concept I am struggling most with is the fact that there are multiple matches that I wish to extract (e.g. 2.0m and 2.4m). I've managed to match on 2.0m, and 2.4m, but how do I determine which one is which? (First High tide vs second high tide).
Any hints?

Answer 1

$string = "High Tide: 2.0m on Mon at 08.54pm and 2.4m on Tue at 09.18am";
preg_match_all("~((High|Low) Tide:)? (\d.\dm) on (\w{3}) at (.{7})~", $string, $matches, PREG_SET_ORDER);
var_dump($matches);
outputs
array
0 =>
array
0 => string 'High Tide: 2.0m on Mon at 08.54pm' (length=33)
1 => string 'High Tide:' (length=10)
2 => string 'High' (length=4)
3 => string '2.0m' (length=4)
4 => string 'Mon' (length=3)
5 => string '08.54pm' (length=7)
1 =>
array
0 => string ' 2.4m on Tue at 09.18am' (length=23)
1 => string '' (length=0)
2 => string '' (length=0)
3 => string '2.4m' (length=4)
4 => string 'Tue' (length=3)
5 => string '09.18am' (length=7)
i probably got the thing about the low tide wrong so here is some code without the tide
$string = "High Tide: 2.0m on Mon at 08.54pm and 2.4m on Tue at 09.18am";
preg_match_all("~(\d.\dm) on (\w{3}) at (.{7})~", $string, $matches, PREG_SET_ORDER);
var_dump($matches);
outputs:
array
0 =>
array
0 => string '2.0m on Mon at 08.54pm' (length=22)
1 => string '2.0m' (length=4)
2 => string 'Mon' (length=3)
3 => string '08.54pm' (length=7)
1 =>
array
0 => string '2.4m on Tue at 09.18am' (length=22)
1 => string '2.4m' (length=4)
2 => string 'Tue' (length=3)
3 => string '09.18am' (length=7)

Answer 2

If the word and always separates the two tides, you could break the string in two and process each half separately. For example:
$str = "High Tide: 2.0m on Mon at 08.54pm and 2.4m on Tue at 09.18am";
$data = explode(" and ", $str);
$result = array();
foreach($data as $tide)
{
$result[] = parseWithRegex($tide);
}

Answer 3

You can use named capturing groups to get an associative array with the result and the pattern to match the string is pretty straight forward.
/(?P<tide>high|low)\s+tide:\s+(?P<height1>\d+\.\d+m)\s+on\s+(?P<day1>[a-z]+)\s+at\s+(?P<time1>\d+\.\d+[ap]m)\s+and\s+(?P<height2>\d+\.\d+m)\s+on\s+(?P<day2>[a-z]+)\s+at\s+(?P<time2>\d+\.\d+[ap]m)/i
Example script:
$string = "High Tide: 2.0m on Mon at 08.54pm and 2.4m on Tue at 09.18am";
// named groups will also assign matches associative to the matches array, e.g. (?P<tide>high|low) will set $matches["tide"] to 'low' or 'high'
preg_match(
'/
(?P<tide>high|low) # match and capture string "high" or "low"
\s+tide:\s+ # match string "tide" surrounded with one or more spaces on each side
(?P<height1>\d+\.\d+m) # match and capture one or more digits followed by a dot and one or more digits followed by an m
\s+on\s+ # match string "on" surrounded with one or more spaces on each side
(?P<day1>[a-z]+) # match one or more letters
\s+at\s+ # match string "at" surrounded with one or more spaces on each side
(?P<time1>\d+\.\d+[ap]m) # match and capture one or more digits followed by a dot and one or more digits followed by an a or p, and string "m", so am or pm
\s+and\s+ # match string "and" surrounded with one or more spaces on each side
(?P<height2>\d+\.\d+m) # match and capture one or more digits followed by a dot and one or more digits followed by an m
\s+on\s+ # match string "on" surrounded with one or more spaces on each side
(?P<day2>[a-z]+) # match one or more letters
\s+at\s+ # match string "at" surrounded with one or more spaces on each side
(?P<time2>\d+\.\d+[ap]m) # match and capture one or more digits followed by a dot and one or more digits followed by an a or p, and string "m", so am or pm
/ix', $string, $matches);
print_r($matches);
this will print
Array
(
[0] => High Tide: 2.0m on Mon at 08.54pm and 2.4m on Tue at 09.18am
[tide] => High
[1] => High
[height1] => 2.0m
[2] => 2.0m
[day1] => Mon
[3] => Mon
[time1] => 08.54pm
[4] => 08.54pm
[height2] => 2.4m
[5] => 2.4m
[day2] => Tue
[6] => Tue
[time2] => 09.18am
[7] => 09.18am
)

Answer 4

you can used named groups and then refer to what you captured by name: (?P<name>exp) => $yourVarName['name']
(not tested, but this would be the idea)
/^[^\d]+(?P<heightOne>[\d\.]+?m)\son\s(?P<dayOne>\w+?)\sat\s(?P<timeOne>.*?(am|pm))\sand\s(?P<heightTwo>[\d\.]+?m)\son\s(?P<dayTwo>\w+?)\sat\s(?P<timeTwo>.*?(am|pm))$/