Fix #78003: strip_tags output change since PHP 7.3

A refactoring of the strip tags state machine[1] missed the special
treatment of `depth > 0` when a `>` is encountered in state 2 or 3.  We
re-add it for BC reasons.

[1] <http://git.php.net/?p=php-src.git;a=commit;h=5cf64742773ddbf9af69d962a4d12b567fcf0084>

Author: cmb69

NEWS

@@ -35,6 +35,7 @@ PHP                                                                        NEWS
 
 - Standard:
   . Fixed bug #77931 (Warning for array_map mentions wrong type). (Nikita)
+  . Fixed bug #78003 (strip_tags output change since PHP 7.3). (cmb)
 
 02 May 2019, PHP 7.3.5
 

ext/standard/string.c

@@ -5227,6 +5227,10 @@ PHPAPI size_t php_strip_tags_ex(char *rbuf, size_t len, uint8_t *stateptr, const
 			}
 			break;
 		case '>':
+			if (depth) {
+				depth--;
+				break;
+			}
 			if (in_q) {
 				break;
 			}
@@ -5284,6 +5288,10 @@ PHPAPI size_t php_strip_tags_ex(char *rbuf, size_t len, uint8_t *stateptr, const
 	c = *p;
 	switch (c) {
 		case '>':
+			if (depth) {
+				depth--;
+				break;
+			}
 			if (in_q) {
 				break;
 			}

ext/standard/tests/strings/bug78003.phpt

@@ -0,0 +1,16 @@
+--TEST--
+Bug #78003 (strip_tags output change since PHP 7.3)
+--FILE--
+<?php
+var_dump(
+    strip_tags('<foo<>bar>'),
+    strip_tags('<foo<!>bar>'),
+    strip_tags('<foo<?>bar>')
+);
+?>
+===DONE===
+--EXPECT--
+string(0) ""
+string(0) ""
+string(0) ""
+===DONE===