Fix enabling of JIT at runtime

Fixes GH-14267

Author: iluuu1994

ext/opcache/jit/zend_jit.c

@@ -4785,12 +4785,12 @@ ZEND_EXT_API int zend_jit_config(zend_string *jit, int stage)
 		return FAILURE;
 	}
 
-	if (ZSTR_LEN(jit) == 0
-	 || zend_string_equals_literal_ci(jit, "disable")) {
+	if (zend_string_equals_literal_ci(jit, "disable")) {
 		JIT_G(enabled) = 0;
 		JIT_G(on) = 0;
 		return SUCCESS;
-	} else if (zend_string_equals_literal_ci(jit, "0")
+	} else if (ZSTR_LEN(jit) == 0
+			|| zend_string_equals_literal_ci(jit, "0")
 			|| zend_string_equals_literal_ci(jit, "off")
 			|| zend_string_equals_literal_ci(jit, "no")
 			|| zend_string_equals_literal_ci(jit, "false")) {

ext/opcache/tests/jit/gh14267_001.phpt

@@ -0,0 +1,16 @@
+--TEST--
+GH-14267: JIT cannot be enabled at runtime
+--INI--
+opcache.enable=1
+opcache.enable_cli=1
+opcache.jit=off
+opcache.jit_buffer_size=32M
+--EXTENSIONS--
+opcache
+--FILE--
+<?php
+ini_set('opcache.jit', 'tracing');
+?>
+===DONE===
+--EXPECT--
+===DONE===

ext/opcache/tests/jit/gh14267_002.phpt

@@ -0,0 +1,15 @@
+--TEST--
+GH-14267: JIT cannot be enabled at runtime
+--INI--
+opcache.enable=1
+opcache.enable_cli=1
+opcache.jit=disable
+opcache.jit_buffer_size=32M
+--EXTENSIONS--
+opcache
+--FILE--
+<?php
+ini_set('opcache.jit', 'tracing');
+?>
+--EXPECTF--
+Warning: Cannot change opcache.jit setting at run-time (JIT is disabled) in %s on line %d