minor #19711 [ExpressionLanguage] Update the docs about the null-coalescing operator (javiereguiluz)

This PR was squashed before being merged into the 6.4 branch.

Discussion
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[ExpressionLanguage] Update the docs about the null-coalescing operator

Fixes #19695.

Commits
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ca016d7 [ExpressionLanguage] Update the docs about the null-coalescing operator

Author: javiereguiluz

components/expression_language.rst

@@ -80,19 +80,10 @@ The main class of the component is
 Null Coalescing Operator
 ........................
 
-This is the same as the PHP `null-coalescing operator`_, which combines
-the ternary operator and ``isset()``. It returns the left hand-side if it exists
-and it's not ``null``; otherwise it returns the right hand-side. Note that you
-can chain multiple coalescing operators.
-
-* ``foo ?? 'no'``
-* ``foo.baz ?? 'no'``
-* ``foo[3] ?? 'no'``
-* ``foo.baz ?? foo['baz'] ?? 'no'``
-
-.. versionadded:: 6.2
+.. note::
 
-    The null-coalescing operator was introduced in Symfony 6.2.
+    This content has been moved to the ref:`null coalescing operator <component-expression-null-coalescing-operator>`
+    section of ExpressionLanguage syntax reference page.
 
 Parsing and Linting Expressions
 ...............................

reference/formats/expression_language.rst

@@ -99,6 +99,8 @@ JavaScript::
 
 This will print out ``Hi Hi Hi!``.
 
+.. _component-expression-null-safe-operator:
+
 Null-safe Operator
 ..................
 
@@ -118,6 +120,29 @@ operator)::
 
     The null safe operator was introduced in Symfony 6.1.
 
+.. _component-expression-null-coalescing-operator:
+
+Null-Coalescing Operator
+........................
+
+It returns the left-hand side if it exists and it's not ``null``; otherwise it
+returns the right-hand side. Expressions can chain multiple coalescing operators:
+
+* ``foo ?? 'no'``
+* ``foo.baz ?? 'no'``
+* ``foo[3] ?? 'no'``
+* ``foo.baz ?? foo['baz'] ?? 'no'``
+
+.. note::
+
+    The main difference with the `null-coalescing operator in PHP`_ is that
+    ExpressionLanguage will throw an exception when trying to access a
+    non-existent variable.
+
+.. versionadded:: 6.2
+
+    The null-coalescing operator was introduced in Symfony 6.2.
+
 .. _component-expression-functions:
 
 Working with Functions
@@ -391,6 +416,12 @@ Ternary Operators
 * ``foo ?: 'no'`` (equal to ``foo ? foo : 'no'``)
 * ``foo ? 'yes'`` (equal to ``foo ? 'yes' : ''``)
 
+Other Operators
+~~~~~~~~~~~~~~~
+
+* ``?.`` (:ref:`null-safe operator <component-expression-null-safe-operator>`)
+* ``??`` (:ref:`null-coalescing operator <component-expression-null-coalescing-operator>`)
+
 Built-in Objects and Variables
 ------------------------------
 
@@ -401,3 +432,5 @@ expressions (e.g. the request, the current user, etc.):
 * :doc:`Variables available in security expressions </security/expressions>`;
 * :doc:`Variables available in service container expressions </service_container/expression_language>`;
 * :ref:`Variables available in routing expressions <routing-matching-expressions>`.
+
+.. _`null-coalescing operator in PHP`: https://www.php.net/manual/en/language.operators.comparison.php#language.operators.comparison.coalesce