PHP - Regex optimization split string in parts - php

Question

In PHP I try to make a regex to split a string in different parts as array elements.
For example this are my strings :
$string1 = "For a serving of 100 g Sugars: 2.3 g (Approximately)";
$string2 = "For a serving of 100 g Saturated Fat: 5.8 g (Approximately)";
$string3 = "For a portion of 100 g Energy Value: 290 kcal (Approximately)";
And I want to extract specific informations from these strings :
$arrayString1 = array('100 g','Sugars', '2.3 g');
$arrayString2 = array('100 g','Saturated Fat', '5.8 g');
$arrayString3 = array('100 g','Energy Value', '290 kcal');
I made this regex :
(^For a serving of )([\d g]*)([^:]*)(: )([\d.\d]*)( )([a-z]*)
Do you have any idea how to optimize this regex?
Thanks

Answer 1

You could make it a bit more specific matching the g or kcal and the digits.
To match all examples, you can use an alternation to match either of the alternatives (?:serving|portion)
Instead of using 7 capturing groups, you can use 3 capturing groups.
You can omit the first capturing group (^For a serving of )and combine the values of the digits and the unit.
^For\h+a\h+(?:serving|portion)\h+of\h+(\d+\h+g)\h+([^:\r\n]+):\h+(\d+(?:\.\d+)? (?:g|kcal))\b
^ Start of string
For\h+a\h+(?:serving|portion)\h+of\h+ Match the beginning of the string with either serving or portion
(\d+\h+g)\h+ Capture group 1, match 1+ digits and g
([^:\r\n]+):\h+ Capture group 2, match 1+ times any char except :, followed by matching : and 1+ horizontal whitspace chars
( Capture group 3
\d+(?:\.\d+)? Match 1+ digits with an optional decimal part
\h+(?:g|kcal) Match 1+ horizontal whitespace chars and either g or kcal
)\b Close group 3 and a word boundary to prevent the word being part of a longer word
Regex demo | Php demo
For example
$pattern = "~^For\h+a\h+(?:serving|portion)\h+of\h+(\d+\h+g)\h+([^:\r\n]+):\h+(\d+(?:\.\d+)?\h+(?:g|kcal))\b~";
$strings = [
"For a serving of 100 g Sugars: 2.3 g (Approximately)",
"For a serving of 100 g Saturated Fat: 5.8 g (Approximately)",
"For a portion of 100 g Energy Value: 290 kcal (Approximately)"
];
foreach ($strings as $string) {
preg_match($pattern, $string, $matches);
array_shift($matches);
print_r($matches);
}
Output
Array
(
[0] => 100 g
[1] => Sugars
[2] => 2.3 g
)
Array
(
[0] => 100 g
[1] => Saturated Fat
[2] => 5.8 g
)
Array
(
[0] => 100 g
[1] => Energy Value
[2] => 290 kcal
)