PHP ActiveX

Regular Expression with Named Capture Groups

See more Regular Expressions Examples

Demonstrates regular expressions with named capture groups.

See the sample code below.

Note: Chilkat uses PCRE2. See PCRE2 Regular Expressions
Also see: PCRE2 Performance

In PCRE2, named capture groups allow you to assign a name to a capturing group, making it easier to reference by name instead of number.

Syntax

(?<name>pattern)

or

(?'name'pattern)

Example

(?<first>\w+)\s+(?<last>\w+)

Applied to:

"John Smith"

Produces:

• first: John
• last: Smith

PHP ActiveX

<?php

$success = 0;

$subject = 'John Smith';
$pattern = '(?<first>\\w+)\\s+(?<last>\\w+)';

$sb = new COM("Chilkat.StringBuilder");
$sb->Append($subject);

$json = new COM("Chilkat.JsonObject");
$json->EmitCompact = 0;

$timeoutMs = 2000;
$numMatches = $sb->RegexMatch($pattern,$json,$timeoutMs);
if ($numMatches < 0) {
    // Probably an error in the regular expression.
    // Suggestion: Use AI to help create and/or diagnose regular expressions.
    print $sb->LastErrorText . "\n";
    exit;
}

// Examine the matches:
print $json->emit() . "\n";

// Here is the JSON showing the matches.
// Important:  Capture group 0 always contains the entire match — that is, the portion of the input string that matches the full regular expression.

// {
//   "named": {
//     "first": 1,
//     "last": 2
//   },
//   "match": [
//     {
//       "group": [
//         {
//           "cap": "John Smith",
//           "idx": 0,
//           "len": 10
//         },
//         {
//           "cap": "John",
//           "idx": 0,
//           "len": 4
//         },
//         {
//           "cap": "Smith",
//           "idx": 5,
//           "len": 5
//         }
//       ]
//     }
//   ]
// }

// The capture group index is obtained by looking up the name in the JSON result.
// For example:

$json->I = $json->IntOf('named.first');
print 'first: ' . $json->stringOf('match[0].group[i].cap') . "\n";

$json->I = $json->IntOf('named.last');
print 'last: ' . $json->stringOf('match[0].group[i].cap') . "\n";

// Output is: 

// first: John
// last: Smith

?>