I have the following string:
[11:36:19] Touched down at -56 fpm, gear lever: down, pitch: 3, roll: level, 116 kts
And I'm trying a regular expression to get the value 116 kts, and the string does not have a fixed number of words.
My expression is this:
\[([0-9:]+)\] Touched down at -[0-9]+ fpm, gear lever: down, pitch: 3, roll: level, [0-9]+ kts/
However, pitch and roll values do not always appear, and this generates the error.
You do not need to specify the entire line in the expression if you want the value of "kts", the expression ([0-9]+) kts (one or more numbers followed by "kts") is sufficient for this line. In PHP, use the preg_match function and pass an array to serve as an output:
$linha = '[11:36:19] Touched down at -56 fpm, gear lever: down, pitch: 3, roll: level, 116 kts';
$saida = array();
preg_match('/([0-9]+) kts/', $linha, $saida);
echo $saida[1];
116
All values marked with parentheses in the regular expression (the so-called "catch group", or rematch ) will be returned in the array. The $saida[0] item always contains the text that matches the whole expression. So, you can populate a single array with all the data you want to extract:
$linha = '[11:36:19] Touched down at -56 fpm, gear lever: down, pitch: 3, roll: level, 116 kts';
$saida = array();
preg_match('/\[([0-9:]+)\] .* ([-+0-9]+) fpm, gear lever: ([a-z]+), pitch: ([0-9]+), roll: ([a-z]+), ([0-9]+) kts/', $linha, $saida);
print_r($saida);
Array
(
[0] => [11:36:19] Touched down at -56 fpm, gear lever: down, pitch: 3, roll: level, 116 kts
[1] => 11:36:19
[2] => -56
[3] => down
[4] => 3
[5] => level
[6] => 116
)
PHP example in repl.it: link
Example of the second regular expression in regex101: link