From 64b21f65ffd545d43d276eaa8c938e14517a8bb6 Mon Sep 17 00:00:00 2001
From: Benjamin Morel <benjamin.morel@gmail.com>
Date: Fri, 16 Nov 2018 16:32:02 +0100
Subject: [PATCH] Autogenerate the Travis CI build matrix with a script

---
 .travis.yml               | 310 ++++++++++++++-----------------------
 travis-matrix-builder.php | 314 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 425 insertions(+), 199 deletions(-)
 create mode 100644 travis-matrix-builder.php

diff --git a/.travis.yml b/.travis.yml
index 49fb1d6f77b..eb9892d7146 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -3,20 +3,9 @@ sudo: false
 dist: trusty
 
 cache:
-    directories:
-        - vendor
-        - $HOME/.composer/cache
-
-php:
-  - 7.1
-  - 7.2
-  - 7.3
-  - nightly
-
-env:
-  - DB=sqlite
-  - DB=mysql
-  - DB=mysqli
+  directories:
+    - vendor
+    - $HOME/.composer/cache
 
 before_install:
   - |
@@ -51,44 +40,31 @@ after_script:
       travis_retry php ocular.phar code-coverage:upload --format=php-clover clover.xml
     fi
 
-jobs:
+matrix:
   allow_failures:
     - php: nightly
     - env: DB=pgsql POSTGRESQL_VERSION=11.0
+    - php: 7.3
+      env: DB=ibm_db2
 
-  exclude:
-    - php: 7.1
-      env: DB=sqlite
-    - php: 7.1
-      env: DB=mysql
-    - php: 7.1
-      env: DB=mysqli
-    - php: 7.2
-      env: DB=sqlite
-    - php: 7.2
-      env: DB=mysql
-    - php: 7.2
-      env: DB=mysqli
+jobs:
+  allow_failures:
+    - php: nightly
+    - env: DB=pgsql POSTGRESQL_VERSION=11.0
+    - php: 7.3
+      env: DB=ibm_db2
 
   include:
-    - stage: Test
-      php: 7.1
-      env: DB=sqlite COVERAGE=yes
-
-    - stage: Test
-      php: 7.1
-      env: DB=mysql COVERAGE=yes
-
-    - stage: Test
-      php: 7.1
-      env: DB=mysqli COVERAGE=yes
-
+# BEGIN TEST BUILD MATRIX - DO NOT EDIT BELOW ▼▼▼ USE THE TRAVIS MATRIX BUILDER SCRIPT
     - stage: Test
       php: 7.1
       env: DB=mysql MYSQL_VERSION=5.7 COVERAGE=yes
       sudo: required
       before_script:
         - bash ./tests/travis/install-mysql-5.7.sh
+    - stage: Test
+      php: 7.2
+      env: DB=mysql
     - stage: Test
       php: 7.2
       env: DB=mysql MYSQL_VERSION=5.7
@@ -107,13 +83,15 @@ jobs:
       sudo: required
       before_script:
         - bash ./tests/travis/install-mysql-5.7.sh
-
     - stage: Test
       php: 7.1
       env: DB=mysqli MYSQL_VERSION=5.7 COVERAGE=yes
       sudo: required
       before_script:
         - bash ./tests/travis/install-mysql-5.7.sh
+    - stage: Test
+      php: 7.2
+      env: DB=mysqli
     - stage: Test
       php: 7.2
       env: DB=mysqli MYSQL_VERSION=5.7
@@ -132,101 +110,84 @@ jobs:
       sudo: required
       before_script:
         - bash ./tests/travis/install-mysql-5.7.sh
-
     - stage: Test
       php: 7.1
-      env: DB=mariadb MARIADB_VERSION=10.0 COVERAGE=yes
+      env: DB=mariadb MARIADB_VERSION=10.3 COVERAGE=yes
       addons:
-        mariadb: 10.0
+        mariadb: 10.3
     - stage: Test
       php: 7.2
       env: DB=mariadb MARIADB_VERSION=10.0
       addons:
         mariadb: 10.0
-    - stage: Test
-      php: nightly
-      env: DB=mariadb MARIADB_VERSION=10.0
-      addons:
-        mariadb: 10.0
-
-    - stage: Test
-      php: 7.1
-      env: DB=mariadb MARIADB_VERSION=10.1 COVERAGE=yes
-      addons:
-        mariadb: 10.1
     - stage: Test
       php: 7.2
       env: DB=mariadb MARIADB_VERSION=10.1
       addons:
         mariadb: 10.1
     - stage: Test
-      php: nightly
-      env: DB=mariadb MARIADB_VERSION=10.1
-      addons:
-        mariadb: 10.1
-
-    - stage: Test
-      php: 7.1
-      env: DB=mariadb MARIADB_VERSION=10.2 COVERAGE=yes
+      php: 7.2
+      env: DB=mariadb MARIADB_VERSION=10.2
       addons:
         mariadb: 10.2
     - stage: Test
       php: 7.2
-      env: DB=mariadb MARIADB_VERSION=10.2
+      env: DB=mariadb MARIADB_VERSION=10.3
       addons:
-        mariadb: 10.2
+        mariadb: 10.3
+    - stage: Test
+      php: 7.3
+      env: DB=mariadb MARIADB_VERSION=10.3
+      addons:
+        mariadb: 10.3
     - stage: Test
       php: nightly
-      env: DB=mariadb MARIADB_VERSION=10.2
+      env: DB=mariadb MARIADB_VERSION=10.3
       addons:
-        mariadb: 10.2
-
+        mariadb: 10.3
     - stage: Test
       php: 7.1
-      env: DB=mariadb.mysqli MARIADB_VERSION=10.2 COVERAGE=yes
+      env: DB=mariadb.mysqli MARIADB_VERSION=10.3 COVERAGE=yes
       addons:
-        mariadb: 10.2
+        mariadb: 10.3
     - stage: Test
       php: 7.2
-      env: DB=mariadb.mysqli MARIADB_VERSION=10.2
+      env: DB=mariadb.mysqli MARIADB_VERSION=10.0
       addons:
-        mariadb: 10.2
+        mariadb: 10.0
     - stage: Test
-      php: nightly
+      php: 7.2
+      env: DB=mariadb.mysqli MARIADB_VERSION=10.1
+      addons:
+        mariadb: 10.1
+    - stage: Test
+      php: 7.2
       env: DB=mariadb.mysqli MARIADB_VERSION=10.2
       addons:
         mariadb: 10.2
-
     - stage: Test
       php: 7.2
-      env: DB=mariadb MARIADB_VERSION=10.3
+      env: DB=mariadb.mysqli MARIADB_VERSION=10.3
       addons:
-          mariadb: 10.3
-
+        mariadb: 10.3
     - stage: Test
       php: 7.3
-      env: DB=mariadb MARIADB_VERSION=10.3
-      addons:
-          mariadb: 10.3
-
-    - stage: Test
-      php: 7.2
       env: DB=mariadb.mysqli MARIADB_VERSION=10.3
       addons:
-          mariadb: 10.3
+        mariadb: 10.3
     - stage: Test
-      php: 7.3
+      php: nightly
       env: DB=mariadb.mysqli MARIADB_VERSION=10.3
       addons:
-          mariadb: 10.3
-
+        mariadb: 10.3
     - stage: Test
       php: 7.1
-      env: DB=pgsql POSTGRESQL_VERSION=9.2 COVERAGE=yes
+      env: DB=pgsql POSTGRESQL_VERSION=11.0 COVERAGE=yes
+      sudo: required
       services:
-        - postgresql
-      addons:
-        postgresql: "9.2"
+        - docker
+      before_script:
+        - bash ./tests/travis/install-postgres-11.sh
     - stage: Test
       php: 7.2
       env: DB=pgsql POSTGRESQL_VERSION=9.2
@@ -234,21 +195,6 @@ jobs:
         - postgresql
       addons:
         postgresql: "9.2"
-    - stage: Test
-      php: nightly
-      env: DB=pgsql POSTGRESQL_VERSION=9.2
-      services:
-        - postgresql
-      addons:
-        postgresql: "9.2"
-
-    - stage: Test
-      php: 7.1
-      env: DB=pgsql POSTGRESQL_VERSION=9.3 COVERAGE=yes
-      services:
-        - postgresql
-      addons:
-        postgresql: "9.3"
     - stage: Test
       php: 7.2
       env: DB=pgsql POSTGRESQL_VERSION=9.3
@@ -256,21 +202,6 @@ jobs:
         - postgresql
       addons:
         postgresql: "9.3"
-    - stage: Test
-      php: nightly
-      env: DB=pgsql POSTGRESQL_VERSION=9.3
-      services:
-        - postgresql
-      addons:
-        postgresql: "9.3"
-
-    - stage: Test
-      php: 7.1
-      env: DB=pgsql POSTGRESQL_VERSION=9.4 COVERAGE=yes
-      services:
-        - postgresql
-      addons:
-        postgresql: "9.4"
     - stage: Test
       php: 7.2
       env: DB=pgsql POSTGRESQL_VERSION=9.4
@@ -278,21 +209,6 @@ jobs:
         - postgresql
       addons:
         postgresql: "9.4"
-    - stage: Test
-      php: nightly
-      env: DB=pgsql POSTGRESQL_VERSION=9.4
-      services:
-        - postgresql
-      addons:
-        postgresql: "9.4"
-
-    - stage: Test
-      php: 7.1
-      env: DB=pgsql POSTGRESQL_VERSION=9.5 COVERAGE=yes
-      services:
-        - postgresql
-      addons:
-        postgresql: "9.5"
     - stage: Test
       php: 7.2
       env: DB=pgsql POSTGRESQL_VERSION=9.5
@@ -300,21 +216,6 @@ jobs:
         - postgresql
       addons:
         postgresql: "9.5"
-    - stage: Test
-      php: nightly
-      env: DB=pgsql POSTGRESQL_VERSION=9.5
-      services:
-        - postgresql
-      addons:
-        postgresql: "9.5"
-
-    - stage: Test
-      php: 7.1
-      env: DB=pgsql POSTGRESQL_VERSION=9.6 COVERAGE=yes
-      services:
-        - postgresql
-      addons:
-        postgresql: "9.6"
     - stage: Test
       php: 7.2
       env: DB=pgsql POSTGRESQL_VERSION=9.6
@@ -322,24 +223,6 @@ jobs:
         - postgresql
       addons:
         postgresql: "9.6"
-    - stage: Test
-      php: nightly
-      env: DB=pgsql POSTGRESQL_VERSION=9.6
-      services:
-        - postgresql
-      addons:
-        postgresql: "9.6"
-
-    - stage: Test
-      php: 7.1
-      env: DB=pgsql POSTGRESQL_VERSION=10.0 COVERAGE=yes
-      sudo: required
-      services:
-        - postgresql
-      addons:
-        postgresql: "9.6"
-      before_script:
-        - bash ./tests/travis/install-postgres-10.sh
     - stage: Test
       php: 7.2
       env: DB=pgsql POSTGRESQL_VERSION=10.0
@@ -350,25 +233,6 @@ jobs:
         postgresql: "9.6"
       before_script:
         - bash ./tests/travis/install-postgres-10.sh
-    - stage: Test
-      php: nightly
-      env: DB=pgsql POSTGRESQL_VERSION=10.0
-      sudo: required
-      services:
-        - postgresql
-      addons:
-        postgresql: "9.6"
-      before_script:
-        - bash ./tests/travis/install-postgres-10.sh
-
-    - stage: Test
-      php: 7.1
-      env: DB=pgsql POSTGRESQL_VERSION=11.0
-      sudo: required
-      services:
-        - docker
-      before_script:
-        - bash ./tests/travis/install-postgres-11.sh
     - stage: Test
       php: 7.2
       env: DB=pgsql POSTGRESQL_VERSION=11.0
@@ -393,14 +257,26 @@ jobs:
         - docker
       before_script:
         - bash ./tests/travis/install-postgres-11.sh
-
     - stage: Test
+      php: 7.1
+      env: DB=sqlite COVERAGE=yes
+    - stage: Test
+      php: 7.2
+      env: DB=sqlite
+    - stage: Test
+      php: 7.3
+      env: DB=sqlite
+    - stage: Test
+      php: nightly
+      env: DB=sqlite
+    - stage: Test
+      php: 7.1
       env: DB=sqlsrv COVERAGE=yes
       sudo: required
       services:
         - docker
       before_script:
-        - bash ./tests/travis/install-mssql-$DB.sh
+        - bash ./tests/travis/install-mssql-sqlsrv.sh
         - bash ./tests/travis/install-mssql.sh
     - stage: Test
       php: 7.2
@@ -409,7 +285,7 @@ jobs:
       services:
         - docker
       before_script:
-        - bash ./tests/travis/install-mssql-$DB.sh
+        - bash ./tests/travis/install-mssql-sqlsrv.sh
         - bash ./tests/travis/install-mssql.sh
     - stage: Test
       php: 7.3
@@ -418,9 +294,17 @@ jobs:
       services:
         - docker
       before_script:
-        - bash ./tests/travis/install-mssql-$DB.sh
+        - bash ./tests/travis/install-mssql-sqlsrv.sh
+        - bash ./tests/travis/install-mssql.sh
+    - stage: Test
+      php: nightly
+      env: DB=sqlsrv
+      sudo: required
+      services:
+        - docker
+      before_script:
+        - bash ./tests/travis/install-mssql-sqlsrv.sh
         - bash ./tests/travis/install-mssql.sh
-
     - stage: Test
       php: 7.1
       env: DB=pdo_sqlsrv COVERAGE=yes
@@ -428,7 +312,7 @@ jobs:
       services:
         - docker
       before_script:
-        - bash ./tests/travis/install-mssql-$DB.sh
+        - bash ./tests/travis/install-mssql-pdo_sqlsrv.sh
         - bash ./tests/travis/install-mssql.sh
     - stage: Test
       php: 7.2
@@ -437,7 +321,7 @@ jobs:
       services:
         - docker
       before_script:
-        - bash ./tests/travis/install-mssql-$DB.sh
+        - bash ./tests/travis/install-mssql-pdo_sqlsrv.sh
         - bash ./tests/travis/install-mssql.sh
     - stage: Test
       php: 7.3
@@ -446,17 +330,26 @@ jobs:
       services:
         - docker
       before_script:
-        - bash ./tests/travis/install-mssql-$DB.sh
+        - bash ./tests/travis/install-mssql-pdo_sqlsrv.sh
         - bash ./tests/travis/install-mssql.sh
-
     - stage: Test
+      php: nightly
+      env: DB=pdo_sqlsrv
+      sudo: required
+      services:
+        - docker
+      before_script:
+        - bash ./tests/travis/install-mssql-pdo_sqlsrv.sh
+        - bash ./tests/travis/install-mssql.sh
+    - stage: Test
+      php: 7.1
       env: DB=ibm_db2 COVERAGE=yes
       sudo: required
       services:
         - docker
       before_script:
         - bash ./tests/travis/install-db2.sh
-        - bash ./tests/travis/install-db2-$DB.sh
+        - bash ./tests/travis/install-db2-ibm_db2.sh
     - stage: Test
       php: 7.2
       env: DB=ibm_db2
@@ -465,7 +358,26 @@ jobs:
         - docker
       before_script:
         - bash ./tests/travis/install-db2.sh
-        - bash ./tests/travis/install-db2-$DB.sh
+        - bash ./tests/travis/install-db2-ibm_db2.sh
+    - stage: Test
+      php: 7.3
+      env: DB=ibm_db2
+      sudo: required
+      services:
+        - docker
+      before_script:
+        - bash ./tests/travis/install-db2.sh
+        - bash ./tests/travis/install-db2-ibm_db2.sh
+    - stage: Test
+      php: nightly
+      env: DB=ibm_db2
+      sudo: required
+      services:
+        - docker
+      before_script:
+        - bash ./tests/travis/install-db2.sh
+        - bash ./tests/travis/install-db2-ibm_db2.sh
+# END TEST BUILD MATRIX - DO NOT EDIT ABOVE ▲▲▲
 
     - stage: Test
       php: 7.1
diff --git a/travis-matrix-builder.php b/travis-matrix-builder.php
new file mode 100644
index 00000000000..3ab74c33175
--- /dev/null
+++ b/travis-matrix-builder.php
@@ -0,0 +1,314 @@
+<?php
+
+/**
+ * This script builds the .travis.yml build matrix, around these variables:
+ *
+ * - PHP versions
+ * - database drivers
+ * - platform versions
+ *
+ * With the following requirements:
+ *
+ * - the latest stable PHP version is tested against all drivers and platform versions
+ * - other PHP versions are tested against the latest version of the platform for each driver
+ */
+
+/**
+ * The PHP versions to test.
+ */
+$phpVersions = ['7.1', '7.2', '7.3', 'nightly'];
+
+/**
+ * The latest stable PHP version.
+ * All drivers and platform versions will be tested against this PHP version.
+ * All other PHP versions will only test each driver with the latest version of the platform.
+ */
+$latestStablePhpVersion = '7.2';
+
+/**
+ * The PHP version used for code coverage analysis.
+ */
+$coveragePhpVersion = '7.1';
+
+/**
+ * The travis config file name.
+ */
+$travisConfigFileName = '.travis.yml';
+
+/**
+ * The strings that signal the beginning and end of the build matrix in the travis config file.
+ */
+$beginBuildMatrixString = '# BEGIN TEST BUILD MATRIX';
+$endBuildMatrixString = '# END TEST BUILD MATRIX';
+
+/**
+ * The database drivers.
+ *
+ * The key is the driver name ("DB" environment variable).
+ * The value is an array mapping an optional *_VERSION environment variable name to a list of versions.
+ * If one of these versions is NULL, then the environment variable will be skipped in the output.
+ *
+ * This version environment variable array MAY BE EMPTY, and MAY CONTAIN AT MOST ONE environment variable.
+ * THE LATEST PLATFORM VERSION MUST BE THE LAST ENTRY IN THE ARRAY.
+ * This point is extremely important to respect the premises of this script.
+ */
+
+$dbs = [
+    'mysql' => [
+        'MYSQL_VERSION' => [
+            null,
+            '5.7'
+        ]
+    ],
+    'mysqli' => [
+        'MYSQL_VERSION' => [
+            null,
+            '5.7'
+        ]
+    ],
+    'mariadb' => [
+        'MARIADB_VERSION' => [
+            '10.0',
+            '10.1',
+            '10.2',
+            '10.3',
+        ]
+    ],
+    'mariadb.mysqli' => [
+        'MARIADB_VERSION' => [
+            '10.0',
+            '10.1',
+            '10.2',
+            '10.3',
+        ]
+    ],
+    'pgsql' => [
+        'POSTGRESQL_VERSION' => [
+            '9.2',
+            '9.3',
+            '9.4',
+            '9.5',
+            '9.6',
+            '10.0',
+            '11.0'
+        ]
+    ],
+    'sqlite' => [],
+    'sqlsrv' => [],
+    'pdo_sqlsrv' => [],
+    'ibm_db2' => [],
+];
+
+/**
+ * The additional Travis job parameters for specific environment variables.
+ * The keys are expected to be single KEY=VALUE pairs to be matched against the env string built in the matrix.
+ */
+
+$additionalJobParams = [
+    'MYSQL_VERSION=5.7' => [
+        'sudo' => 'required',
+        'before_script' => ['bash ./tests/travis/install-mysql-5.7.sh']
+    ],
+    'POSTGRESQL_VERSION=10.0' => [
+        'sudo' => 'required',
+        'services' => ['postgresql'],
+        'addons' => ['postgresql' => '"9.6"'],
+        'before_script' => ['bash ./tests/travis/install-postgres-10.sh']
+    ],
+    'POSTGRESQL_VERSION=11.0' => [
+        'sudo' => 'required',
+        'services' => ['docker'],
+        'before_script' => ['bash ./tests/travis/install-postgres-11.sh']
+    ],
+    'DB=sqlsrv' => [
+        'sudo' => 'required',
+        'services' => ['docker'],
+        'before_script' => [
+            'bash ./tests/travis/install-mssql-sqlsrv.sh',
+            'bash ./tests/travis/install-mssql.sh'
+        ]
+    ],
+    'DB=pdo_sqlsrv' => [
+        'sudo' => 'required',
+        'services' => ['docker'],
+        'before_script' => [
+            'bash ./tests/travis/install-mssql-pdo_sqlsrv.sh',
+            'bash ./tests/travis/install-mssql.sh'
+        ]
+    ],
+    'DB=ibm_db2' => [
+        'sudo' => 'required',
+        'services' => ['docker'],
+        'before_script' => [
+            'bash ./tests/travis/install-db2.sh',
+            'bash ./tests/travis/install-db2-ibm_db2.sh'
+        ]
+    ]
+];
+
+foreach (['10.0', '10.1', '10.2', '10.3'] as $mariadbVersion) {
+    $additionalJobParams['MARIADB_VERSION=' . $mariadbVersion] = [
+        'addons' => ['mariadb' => $mariadbVersion],
+    ];
+}
+
+foreach (['9.2', '9.3', '9.4', '9.5', '9.6'] as $pgsqlVersion) {
+    $additionalJobParams['POSTGRESQL_VERSION=' . $pgsqlVersion] = [
+        'services' => ['postgresql'],
+        'addons' => ['postgresql' => '"' . $pgsqlVersion . '"'],
+    ];
+}
+
+
+/* Generate jobs */
+
+$jobs = [];
+
+foreach ($dbs as $db => $versions) {
+    if (empty($versions)) {
+        $baseEnvs = [[]];
+    } elseif (count($versions) === 1) {
+        $baseEnvs = [];
+
+        foreach ($versions as $versionEnvName => $versionValues) { // single iteration
+            foreach ($versionValues as $versionValue) {
+                if ($versionValue === null) {
+                    $baseEnvs[] = [];
+                } else {
+                    $baseEnvs[] = [$versionEnvName => $versionValue];
+                }
+            }
+        }
+    } else {
+        echo "Error: this script does not currently support multiple environment variables per database driver.\n";
+        exit(1);
+    }
+
+    foreach ($phpVersions as $phpVersion) {
+        foreach ($baseEnvs as $baseEnvKey => $baseEnv) {
+            $env = ['DB' => $db];
+
+            $isLatestVersion = ($baseEnvKey === count($baseEnvs) - 1);
+
+            foreach ($baseEnv as $envName => $envValue) {  // at most one iteration
+                $env[$envName] = $envValue;
+            }
+
+            if ($phpVersion !== $latestStablePhpVersion && ! $isLatestVersion) {
+                // not the latest stable PHP version: only test the latest platform version
+                continue;
+            }
+
+            if ($phpVersion === $coveragePhpVersion) {
+                $env['COVERAGE'] = 'yes';
+            }
+
+            $env = envArrayToString($env);
+
+            $job = [
+                'stage' => 'Test',
+                'php' => $phpVersion,
+                'env' => $env
+            ];
+
+            foreach ($additionalJobParams as $jobEnvKeyValuePair => $jobParams) {
+                if (strpos($env, $jobEnvKeyValuePair) !== false) {
+                    $job += $jobParams;
+                }
+            }
+
+            $jobs[] = $job;
+        }
+    }
+}
+
+
+/* Write jobs to the Travis config file in YAML format */
+
+$travisYAML = file_get_contents($travisConfigFileName);
+
+if ($travisYAML === false) {
+    echo "Error: could not read Travis config file.\n";
+    exit(1);
+}
+
+$startPos = strpos($travisYAML, $beginBuildMatrixString);
+
+if ($startPos === false) {
+    echo "Error: could not find the $beginBuildMatrixString string in the Travis config file.\n";
+    exit(1);
+}
+
+$startPos = strpos($travisYAML, "\n", $startPos);
+
+if ($startPos === false) {
+    echo "Error: no further content after the $beginBuildMatrixString line.\n";
+    exit(1);
+}
+
+$endPos = strpos($travisYAML, $endBuildMatrixString, $startPos);
+
+if ($endPos === false) {
+    echo "Error: could not find the $endBuildMatrixString string in the Travis config file.\n";
+    exit(1);
+}
+
+$resultYAML  = substr($travisYAML, 0, $startPos + 1);
+$resultYAML .= arrayToYAML($jobs, 2);
+$resultYAML .= substr($travisYAML, $endPos);
+
+$result = file_put_contents($travisConfigFileName, $resultYAML);
+
+if ($result === false) {
+    echo "Error: could not write the $travisConfigFileName file.\n";
+    exit(1);
+}
+
+echo "Successfully written the $travisConfigFileName file.\n";
+
+
+/* Utility functions */
+
+function envArrayToString(array $env) : string
+{
+    $result = [];
+
+    foreach ($env as $key => $value) {
+        $result[] = "$key=$value";
+    }
+
+    return implode(' ', $result);
+}
+
+function arrayToYAML(array $array, int $level = 0, $indentFirst = true) : string
+{
+    $result = '';
+
+    $first = true;
+
+    foreach ($array as $key => $value) {
+        if (! ($first && ! $indentFirst)) {
+            $result .= str_repeat(' ', $level * 2);
+        }
+
+        if (is_int($key)) {
+            $result .= '- ';
+        } else {
+            $result .= $key . ': ';
+        }
+
+        if (is_array($value)) {
+            if (! is_int($key)) {
+                $result .= "\n";
+            }
+
+            $result .= arrayToYAML($value, $level + 1, ! is_int($key));
+        } else {
+            $result .= $value . "\n";
+        }
+
+        $first = false;
+    }
+
+    return $result;
+}