diff --git a/bin/functionMetadata_original.php b/bin/functionMetadata_original.php
index 838d2ecd5c..68e2a1846a 100644
--- a/bin/functionMetadata_original.php
+++ b/bin/functionMetadata_original.php
@@ -98,6 +98,18 @@
 	'mb_str_pad' => ['hasSideEffects' => false],
 	'mkdir' => ['hasSideEffects' => true],
 	'move_uploaded_file' => ['hasSideEffects' => true],
+	'ob_clean' => ['hasSideEffects' => true],
+	'ob_end_clean' => ['hasSideEffects' => true],
+	'ob_end_flush' => ['hasSideEffects' => true],
+	'ob_flush' => ['hasSideEffects' => true],
+	'ob_get_clean' => ['hasSideEffects' => true],
+	'ob_get_contents' => ['hasSideEffects' => true],
+	'ob_get_length' => ['hasSideEffects' => true],
+	'ob_get_level' => ['hasSideEffects' => true],
+	'ob_get_status' => ['hasSideEffects' => true],
+	'ob_list_handlers' => ['hasSideEffects' => true],
+	'output_add_rewrite_var' => ['hasSideEffects' => true],
+	'output_reset_rewrite_vars' => ['hasSideEffects' => true],
 	'pclose' => ['hasSideEffects' => true],
 	'popen' => ['hasSideEffects' => true],
 	'readfile' => ['hasSideEffects' => true],
diff --git a/bin/generate-function-metadata.php b/bin/generate-function-metadata.php
index f6f5131a53..f759d9c844 100755
--- a/bin/generate-function-metadata.php
+++ b/bin/generate-function-metadata.php
@@ -86,6 +86,7 @@ public function enterNode(Node $node)
 					'connection_aborted',
 					'connection_status',
 					'file_get_contents',
+					'ob_get_contents',
 				], true)) {
 					continue;
 				}
diff --git a/resources/functionMetadata.php b/resources/functionMetadata.php
index 4ba615393d..a32a806e41 100644
--- a/resources/functionMetadata.php
+++ b/resources/functionMetadata.php
@@ -1382,11 +1382,22 @@
 	'numfmt_get_symbol' => ['hasSideEffects' => false],
 	'numfmt_get_text_attribute' => ['hasSideEffects' => false],
 	'numfmt_parse' => ['hasSideEffects' => false],
+	'ob_clean' => ['hasSideEffects' => true],
+	'ob_end_clean' => ['hasSideEffects' => true],
+	'ob_end_flush' => ['hasSideEffects' => true],
 	'ob_etaghandler' => ['hasSideEffects' => false],
-	'ob_get_contents' => ['hasSideEffects' => false],
+	'ob_flush' => ['hasSideEffects' => true],
+	'ob_get_clean' => ['hasSideEffects' => true],
+	'ob_get_contents' => ['hasSideEffects' => true],
+	'ob_get_length' => ['hasSideEffects' => true],
+	'ob_get_level' => ['hasSideEffects' => true],
+	'ob_get_status' => ['hasSideEffects' => true],
 	'ob_iconv_handler' => ['hasSideEffects' => false],
+	'ob_list_handlers' => ['hasSideEffects' => true],
 	'octdec' => ['hasSideEffects' => false],
 	'ord' => ['hasSideEffects' => false],
+	'output_add_rewrite_var' => ['hasSideEffects' => true],
+	'output_reset_rewrite_vars' => ['hasSideEffects' => true],
 	'pack' => ['hasSideEffects' => false],
 	'pam_auth' => ['hasSideEffects' => false],
 	'pam_chpass' => ['hasSideEffects' => false],