bug symfony#37921 [Yaml] account for is_numeric() behavior changes in PHP 8 (xabbuh)

This PR was merged into the 3.4 branch.

Discussion
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[Yaml] account for is_numeric() behavior changes in PHP 8

| Q             | A
| ------------- | ---
| Branch?       | 3.4
| Bug fix?      | yes
| New feature?  | no
| Deprecations? | no
| Tickets       |
| License       | MIT
| Doc PR        |

Commits
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05db8e0 account for is_numeric() behavior changes in PHP 8

Author: fabpot

src/Symfony/Component/Yaml/Inline.php

@@ -210,7 +210,7 @@ public static function dump($value, $flags = 0)
                 return 'false';
             case ctype_digit($value):
                 return \is_string($value) ? "'$value'" : (int) $value;
-            case is_numeric($value):
+            case is_numeric($value) && false === strpos($value, "\n"):
                 $locale = setlocale(LC_NUMERIC, 0);
                 if (false !== $locale) {
                     setlocale(LC_NUMERIC, 'C');