Fix #78441: Parse error due to heredoc identifier followed by digit

Since digits are allowed for identifiers, we have to cater to them as
well.

Author: cmb69

NEWS

@@ -6,6 +6,8 @@ PHP                                                                        NEWS
   . Fixed bug #78220 (Can't access OneDrive folder). (cmb, ab)
   . Fixed bug #77922 (Double release of doc comment on inherited shadow
     property). (Nikita)
+  . Fixed bug #78441 (Parse error due to heredoc identifier followed by digit).
+    (cmb)
 
 - Intl:
   . Ensure IDNA2003 rules are used with idn_to_ascii() and idn_to_utf8()

Zend/tests/grammar/bug78441.phpt

@@ -0,0 +1,24 @@
+--TEST--
+Bug #78441 (Parse error due to heredoc identifier followed by digit)
+--FILE--
+<?php
+echo <<<FOO
+FOO4
+FOO, PHP_EOL;
+
+echo <<<FOO
+bar
+FOO4
+FOO, PHP_EOL;
+
+echo <<<'FOO'
+bar
+FOO4
+FOO, PHP_EOL;
+?>
+--EXPECT--
+FOO4
+bar
+FOO4
+bar
+FOO4