minor #20364 CS: apply rules (keradus)

This PR was squashed before being merged into the 2.7 branch (closes #20364).

Discussion
----------

CS: apply rules

| Q | A |
| --- | --- |
| Branch? | 2.7 |
| Bug fix? | no |
| New feature? | no |
| BC breaks? | no |
| Deprecations? | no |
| Tests pass? | n/a |
| Fixed tickets | - |
| License | MIT |
| Doc PR | - |

Commits
-------

22d4e15 CS: apply rules

Author: nicolas-grekas

Tests/ParserTest.php

@@ -444,7 +444,7 @@ public function testObjectSupportDisabledButNoExceptions($input)
 
     public function testObjectForMapEnabledWithMapping()
     {
-        $yaml = <<<EOF
+        $yaml = <<<'EOF'
 foo:
     fiz: [cat]
 EOF;
@@ -581,7 +581,7 @@ public function testSequenceInAMapping()
 
     public function testSequenceInMappingStartedBySingleDashLine()
     {
-        $yaml = <<<EOT
+        $yaml = <<<'EOT'
 a:
 -
   b:
@@ -609,7 +609,7 @@ public function testSequenceInMappingStartedBySingleDashLine()
 
     public function testSequenceFollowedByCommentEmbeddedInMapping()
     {
-        $yaml = <<<EOT
+        $yaml = <<<'EOT'
 a:
     b:
         - c
@@ -645,7 +645,7 @@ public function testMappingInASequence()
      */
     public function testScalarInSequence()
     {
-        Yaml::parse(<<<EOF
+        Yaml::parse(<<<'EOF'
 foo:
     - bar
 "missing colon"
@@ -666,7 +666,7 @@ public function testScalarInSequence()
      */
     public function testMappingDuplicateKeyBlock()
     {
-        $input = <<<EOD
+        $input = <<<'EOD'
 parent:
     child: first
     child: duplicate
@@ -684,7 +684,7 @@ public function testMappingDuplicateKeyBlock()
 
     public function testMappingDuplicateKeyFlow()
     {
-        $input = <<<EOD
+        $input = <<<'EOD'
 parent: { child: first, child: duplicate }
 parent: { child: duplicate, child: duplicate }
 EOD;
@@ -968,7 +968,7 @@ public function getCommentLikeStringInScalarBlockData()
         );
         $tests[] = array($yaml, $expected);
 
-        $yaml = <<<EOT
+        $yaml = <<<'EOT'
 foo:
   bar:
     scalar-block: >
@@ -1011,7 +1011,7 @@ public function getCommentLikeStringInScalarBlockData()
 
     public function testBlankLinesAreParsedAsNewLinesInFoldedBlocks()
     {
-        $yaml = <<<EOT
+        $yaml = <<<'EOT'
 test: >
     <h2>A heading</h2>
 
@@ -1023,7 +1023,7 @@ public function testBlankLinesAreParsedAsNewLinesInFoldedBlocks()
 
         $this->assertSame(
             array(
-                'test' => <<<EOT
+                'test' => <<<'EOT'
 <h2>A heading</h2>
 <ul> <li>a list</li> <li>may be a good example</li> </ul>
 EOT
@@ -1035,7 +1035,7 @@ public function testBlankLinesAreParsedAsNewLinesInFoldedBlocks()
 
     public function testAdditionallyIndentedLinesAreParsedAsNewLinesInFoldedBlocks()
     {
-        $yaml = <<<EOT
+        $yaml = <<<'EOT'
 test: >
     <h2>A heading</h2>
 
@@ -1047,7 +1047,7 @@ public function testAdditionallyIndentedLinesAreParsedAsNewLinesInFoldedBlocks()
 
         $this->assertSame(
             array(
-                'test' => <<<EOT
+                'test' => <<<'EOT'
 <h2>A heading</h2>
 <ul>
   <li>a list</li>
@@ -1080,7 +1080,7 @@ public function parserThrowsExceptionWithCorrectLineNumberProvider()
         return array(
             array(
                 4,
-                <<<YAML
+                <<<'YAML'
 foo:
     -
         # bar
@@ -1089,7 +1089,7 @@ public function parserThrowsExceptionWithCorrectLineNumberProvider()
             ),
             array(
                 5,
-                <<<YAML
+                <<<'YAML'
 foo:
     -
         # bar
@@ -1099,7 +1099,7 @@ public function parserThrowsExceptionWithCorrectLineNumberProvider()
             ),
             array(
                 8,
-                <<<YAML
+                <<<'YAML'
 foo:
     -
         # foobar
@@ -1112,7 +1112,7 @@ public function parserThrowsExceptionWithCorrectLineNumberProvider()
             ),
             array(
                 10,
-                <<<YAML
+                <<<'YAML'
 foo:
     -
         # foobar

Unescaper.php

@@ -73,7 +73,7 @@ public function unescapeDoubleQuotedString($value)
      */
     public function unescapeCharacter($value)
     {
-        switch ($value{1}) {
+        switch ($value[1]) {
             case '0':
                 return "\x0";
             case 'a':