Add benchmark tracking workflow with GitHub Pages

.github/phpbench_to_json.php

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+<?php
+
+/**
+ * Convert PHPBench XML output to the JSON format expected by
+ * benchmark-action/github-action-benchmark (customSmallerIsBetter).
+ *
+ * Usage:
+ *   php phpbench_to_json.php phpbench.xml > output.json
+ *
+ * The script reads the XML dump produced by PHPBench's --dump-file option
+ * and emits a JSON array where each entry has:
+ *   - name:  benchmark class short name + subject (e.g. "DiagnosticsBench::benchDiagnostics")
+ *   - unit:  "μs" (microseconds)
+ *   - value: mean time in microseconds
+ *   - range: "± {relative standard deviation}%"
+ *   - extra: iteration count and revision count
+ */
+
+if ($argc < 2) {
+    fwrite(STDERR, "Usage: php phpbench_to_json.php <phpbench-dump.xml>\n");
+    exit(1);
+}
+
+$file = $argv[1];
+
+if (!file_exists($file)) {
+    fwrite(STDERR, "Error: file not found: {$file}\n");
+    exit(1);
+}
+
+$xml = simplexml_load_file($file);
+
+if ($xml === false) {
+    fwrite(STDERR, "Error: could not parse XML file: {$file}\n");
+    exit(1);
+}
+
+$results = [];
+
+foreach ($xml->suite as $suite) {
+    foreach ($suite->benchmark as $benchmark) {
+        $className = (string) $benchmark['class'];
+
+        // Use the short class name for readability.
+        $shortName = $className;
+        if (($pos = strrpos($className, '\\')) !== false) {
+            $shortName = substr($className, $pos + 1);
+        }
+
+        foreach ($benchmark->subject as $subject) {
+            $subjectName = (string) $subject['name'];
+
+            foreach ($subject->variant as $variant) {
+                // Build a descriptive name including parameter set if present.
+                $paramDesc = '';
+                if (isset($variant->parameter_set)) {
+                    $params = [];
+                    foreach ($variant->parameter_set->parameter as $param) {
+                        $params[] = (string) $param['value'];
+                    }
+                    if (!empty($params)) {
+                        $paramDesc = ' (' . implode(', ', $params) . ')';
+                    }
+                }
+
+                $name = $shortName . '::' . $subjectName . $paramDesc;
+
+                $stats = $variant->stats;
+
+                if (!$stats) {
+                    // Fall back to computing from iterations if stats element is missing.
+                    $times = [];
+                    foreach ($variant->iteration as $iteration) {
+                        $revs = (int) $iteration['time-revs'];
+                        $netTime = (float) $iteration['time-net'];
+                        // time-net is total time for all revs in microseconds.
+                        $times[] = $revs > 0 ? $netTime / $revs : $netTime;
+                    }
+
+                    if (empty($times)) {
+                        continue;
+                    }
+
+                    $mean = array_sum($times) / count($times);
+                    $rstdev = 0;
+                    if (count($times) > 1 && $mean > 0) {
+                        $variance = 0;
+                        foreach ($times as $t) {
+                            $variance += ($t - $mean) ** 2;
+                        }
+                        $variance /= count($times);
+                        $rstdev = (sqrt($variance) / $mean) * 100;
+                    }
+
+                    $results[] = [
+                        'name' => $name,
+                        'unit' => 'μs',
+                        'value' => round($mean, 3),
+                        'range' => '± ' . round($rstdev, 2) . '%',
+                        'extra' => count($times) . ' iterations',
+                    ];
+                } else {
+                    $mean = (float) $stats['mean'];
+                    $rstdev = (float) $stats['rstdev'];
+                    $iterations = (int) $variant['iterations'];
+                    $revs = (int) $variant['revs'];
+
+                    $results[] = [
+                        'name' => $name,
+                        'unit' => 'μs',
+                        'value' => round($mean, 3),
+                        'range' => '± ' . round($rstdev, 2) . '%',
+                        'extra' => $iterations . ' iterations, ' . $revs . ' revs',
+                    ];
+                }
+            }
+        }
+    }
+}
+
+echo json_encode($results, JSON_PRETTY_PRINT | JSON_UNESCAPED_UNICODE) . "\n";

.github/workflows/benchmark.yml

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+name: Benchmark
+
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+    branches:
+      - master
+
+jobs:
+  benchmark:
+    name: Benchmark
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+    if: github.event_name == 'push' && github.ref == 'refs/heads/master'
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Install PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          coverage: none
+          php-version: "8.1"
+          tools: composer:v2
+
+      - name: Composer install
+        uses: ramsey/composer-install@v2
+        with:
+          composer-options: "--no-scripts"
+
+      - name: Ensure gh-pages branch exists
+        run: |
+          if ! git ls-remote --exit-code --heads origin gh-pages > /dev/null 2>&1; then
+            git config user.name "github-actions[bot]"
+            git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
+            empty_tree="$(git hash-object -t tree /dev/null)"
+            commit="$(git commit-tree "$empty_tree" -m 'Initial gh-pages branch')"
+            git push origin "$commit:refs/heads/gh-pages"
+          fi
+
+      - name: Run PHPBench
+        run: vendor/bin/phpbench run --progress=plain --dump-file=phpbench.xml
+
+      - name: Convert results to JSON
+        run: php .github/phpbench_to_json.php phpbench.xml > output.json
+
+      - name: Store benchmark result
+        uses: benchmark-action/github-action-benchmark@v1
+        with:
+          name: Phpactor Benchmarks
+          tool: customSmallerIsBetter
+          output-file-path: output.json
+          gh-pages-branch: gh-pages
+          benchmark-data-dir-path: dev/bench
+          auto-push: true
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+
+  benchmark-pr:
+    name: Benchmark (PR comparison)
+    runs-on: ubuntu-latest
+    if: github.event_name == 'pull_request'
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Install PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          coverage: none
+          php-version: "8.1"
+          tools: composer:v2
+
+      - name: Composer install
+        uses: ramsey/composer-install@v2
+        with:
+          composer-options: "--no-scripts"
+
+      - name: Check gh-pages branch exists
+        id: check-gh-pages
+        run: |
+          if git ls-remote --exit-code --heads origin gh-pages > /dev/null 2>&1; then
+            echo "exists=true" >> "$GITHUB_OUTPUT"
+          else
+            echo "exists=false" >> "$GITHUB_OUTPUT"
+            echo "⚠️ gh-pages branch does not exist yet — skipping PR benchmark comparison"
+          fi
+
+      - name: Run PHPBench
+        if: steps.check-gh-pages.outputs.exists == 'true'
+        run: vendor/bin/phpbench run --progress=plain --dump-file=phpbench.xml
+
+      - name: Convert results to JSON
+        if: steps.check-gh-pages.outputs.exists == 'true'
+        run: php .github/phpbench_to_json.php phpbench.xml > output.json
+
+      - name: Compare against baseline
+        if: steps.check-gh-pages.outputs.exists == 'true'
+        uses: benchmark-action/github-action-benchmark@v1
+        with:
+          name: Phpactor Benchmarks
+          tool: customSmallerIsBetter
+          output-file-path: output.json
+          gh-pages-branch: gh-pages
+          benchmark-data-dir-path: dev/bench
+          auto-push: false
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          comment-on-alert: true
+          alert-threshold: "130%"
+          fail-on-alert: true