PHP Requires Chilkat v11.1.0+

Regular Expression Replace Capture Groups

See more Regular Expressions Examples

Demonstrates replacing capture groups for a regular expression.

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

Chilkat2 PHP

<?php

use Chilkat2\JsonObject;
use Chilkat2\StringBuilder;

$subject = 'John Anders, +_+_+ Mary Robins $$$$';
$pattern = '(?<first>\w+)\s+(?<last>\w+)';

$sb = new StringBuilder();
$sb->Append($subject);

$json = new JsonObject();
$json->EmitCompact = false;

$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.
    echo $sb->LastErrorText, "\n";
    exit;
}

// Examine the matches:
echo $json->Emit(), "\n";

// There are 2 matches:

// {
//   "named": {
//     "first": 1,
//     "last": 2
//   },
//   "match": [
//     {
//       "group": [
//         {
//           "cap": "John Anders",
//           "idx": 0,
//           "len": 11
//         },
//         {
//           "cap": "John",
//           "idx": 0,
//           "len": 4
//         },
//         {
//           "cap": "Anders",
//           "idx": 5,
//           "len": 6
//         }
//       ]
//     },
//     {
//       "group": [
//         {
//           "cap": "Mary Robins",
//           "idx": 19,
//           "len": 11
//         },
//         {
//           "cap": "Mary",
//           "idx": 19,
//           "len": 4
//         },
//         {
//           "cap": "Robins",
//           "idx": 24,
//           "len": 6
//         }
//       ]
//     }
//   ]
// }

// To replace capture groups, write code to examine each capture group within
// each match, and provide a replacement string.
// Then call RegexReplace.

// For example, let's capitalize the first names, and add append "on" to the last name.
// After doing replacements, we should get:  JOHN Anderson, +_+_+ MARY Robinson $$$$

$firstNameIdx = $json->IntOf('named.first');
$lastNameIdx = $json->IntOf('named.last');

$sbTemp = new StringBuilder();

$i = 0;
$numMatches = $json->SizeOfArray('match');
while ($i < $numMatches) {
    $json->I = $i;

    // The replacement string for the first name will be all uppercase.
    $json->J = $firstNameIdx;
    $sbTemp->Clear();
    $json->StringOfSb('match[i].group[j].cap', $sbTemp);
    $sbTemp->ToUppercase();
    $json->UpdateSb('match[i].group[j].rep', $sbTemp);

    // Append "on" to the last name.
    $json->J = $lastNameIdx;
    $sbTemp->Clear();
    $json->StringOfSb('match[i].group[j].cap', $sbTemp);
    $sbTemp->Append('on');
    $json->UpdateSb('match[i].group[j].rep', $sbTemp);

    $i = $i + 1;
}

// The JSON now has replacement strings:
echo $json->Emit(), "\n";

// {
//   "named": {
//     "first": 1,
//     "last": 2
//   },
//   "match": [
//     {
//       "group": [
//         {
//           "cap": "John Anders",
//           "idx": 0,
//           "len": 11
//         },
//         {
//           "cap": "John",
//           "idx": 0,
//           "len": 4,
//           "rep": "JOHN"
//         },
//         {
//           "cap": "Anders",
//           "idx": 5,
//           "len": 6,
//           "rep": "Anderson"
//         }
//       ]
//     },
//     {
//       "group": [
//         {
//           "cap": "Mary Robins",
//           "idx": 19,
//           "len": 11
//         },
//         {
//           "cap": "Mary",
//           "idx": 19,
//           "len": 4,
//           "rep": "MARY"
//         },
//         {
//           "cap": "Robins",
//           "idx": 24,
//           "len": 6,
//           "rep": "Robinson"
//         }
//       ]
//     }
//   ]
// }

// Call RegexReplace to update the StringBuilder with the replacements.
try {
    $sb->RegexReplace($json);
} catch (\Chilkat2\Exception $e) {
    echo $e->getMessage(), "\n";
    exit;
}

echo "Result after doing replacements:\n";
echo $sb->GetAsString(), "\n";

// Result after doing replacements:
// JOHN Anderson, +_+_+ MARY Robinson $$$$