Question

I have a few regexes in an array and testing some strings against them.

$results = array();

$testString = 'The distance is 0,1 km. It is above 200 m.';

$regex = array(
  'distance' => '/The distance is (?P<distance>\d+) m\./',
  'distance' => '/The distance is (?P<distance>\d+(,\d+)?) km\./',
  'height' => '/It is above (?P<height>\d+) m\./'
  'height' => '/It is above (?P<height>\d+(,\d+)?) km\./'
);

foreach ($regex as $key => $reg) {
  if (preg_match($reg, $testString, $matches)) {
    $results[] = array('type' => $key, 'value' => $matches[$key]);
  }
}

I want to store the results as “meters”, but in the test string above, the “km”-regex is matched.

Can I add some magic to the regex code, so it transforms the matched 0,1 into 100 (= match * 1000)?

It would be perfect to do it right in the regex code, so I dont have to add exceptions into the PHP code.

Thank you for your help! 🙂

Wulf

Answer 1

If you want dirty tricks, you could do something like this after assigning the string:

$testString = preg_replace('/(\d+)(?:,(\d+))?(\s*)km\b/e', '($1.$2 * 1000)."$3m"', $testString);

http://ideone.com/Sk2um

PS: you can’t do that directly in your regex (in PHP anyway), you have to use some code somewhere for it to work.

Explanation: It matches numbers with km after them, capturing the integer and decimal parts, then replacing them with the results of the PHP code in the replacement:

(<integer>.<decimal> * 1000)."<space>m"

The code is evaluated because the /e flag is used.