Merge branch 'PHP-7.4'

* PHP-7.4:
  Avoid duplicate octal warning during heredoc scan ahead

Author: nikic

Zend/tests/warning_during_heredoc_scan_ahead.phpt

@@ -0,0 +1,17 @@
+--TEST--
+No warnings should be thrown during heredoc scan-ahead
+--FILE--
+<?php
+
+<<<TEST
+\400
+${"\400"}
+TEST;
+
+?>
+--EXPECTF--
+Warning: Octal escape sequence overflow \400 is greater than \377 in %s on line %d
+
+Warning: Octal escape sequence overflow \400 is greater than \377 in %s on line %d
+
+Warning: Undefined variable $ in %s on line %d

Zend/zend_language_scanner.l

@@ -1113,8 +1113,7 @@ static zend_result zend_scan_escape_string(zval *zendlval, char *str, int len, c
 								octal_buf[2] = *(++s);
 							}
 						}
-						if (octal_buf[2] &&
-						    (octal_buf[0] > '3')) {
+						if (octal_buf[2] && (octal_buf[0] > '3') && !SCNG(heredoc_scan_ahead)) {
 							/* 3 octit values must not overflow 0xFF (\377) */
 							zend_error(E_COMPILE_WARNING, "Octal escape sequence overflow \\%s is greater than \\377", octal_buf);
 						}