diff --git a/ext/iconv/iconv.c b/ext/iconv/iconv.c
index b61d253c5d4be..157ee41a11a05 100644
--- a/ext/iconv/iconv.c
+++ b/ext/iconv/iconv.c
@@ -63,15 +63,15 @@
 #define PHP_ICONV_IMPL_VALUE "unknown"
 #endif
 
-static char *get_iconv_version(void) {
-	char *version = "unknown";
+static const char *get_iconv_version(void) {
+	const char *version = "unknown";
 
 #ifdef HAVE_LIBICONV
 	static char buf[16];
 	snprintf(buf, sizeof(buf), "%d.%d", _libiconv_version >> 8, _libiconv_version & 0xff);
 	version = buf;
 #elif defined(HAVE_GLIBC_ICONV)
-	version = (char *) gnu_get_libc_version();
+	version = gnu_get_libc_version();
 #endif
 
 	return version;
@@ -243,7 +243,7 @@ PHP_MSHUTDOWN_FUNCTION(miconv)
 /* {{{ PHP_MINFO_FUNCTION */
 PHP_MINFO_FUNCTION(miconv)
 {
-	zval *iconv_impl, *iconv_ver;
+	const zval *iconv_impl, *iconv_ver;
 
 	iconv_impl = zend_get_constant_str("ICONV_IMPL", sizeof("ICONV_IMPL")-1);
 	iconv_ver = zend_get_constant_str("ICONV_VERSION", sizeof("ICONV_VERSION")-1);
@@ -298,17 +298,18 @@ static php_output_handler *php_iconv_output_handler_init(const char *handler_nam
 
 static zend_result php_iconv_output_handler(void **nothing, php_output_context *output_context)
 {
-	char *s, *content_type, *mimetype = NULL;
-	int output_status, mimetype_len = 0;
+	char *content_type, *mimetype = NULL;
 
 	if (output_context->op & PHP_OUTPUT_HANDLER_START) {
-		output_status = php_output_get_status();
+		int output_status = php_output_get_status();
 		if (output_status & PHP_OUTPUT_SENT) {
 			return FAILURE;
 		}
 
+		int mimetype_len = 0;
 		if (SG(sapi_headers).mimetype && !strncasecmp(SG(sapi_headers).mimetype, "text/", 5)) {
-			if ((s = strchr(SG(sapi_headers).mimetype,';')) == NULL){
+			const char *s = strchr(SG(sapi_headers).mimetype,';');
+			if (s == NULL){
 				mimetype = SG(sapi_headers).mimetype;
 			} else {
 				mimetype = SG(sapi_headers).mimetype;
@@ -320,7 +321,7 @@ static zend_result php_iconv_output_handler(void **nothing, php_output_context *
 
 		if (mimetype != NULL && (!(output_context->op & PHP_OUTPUT_HANDLER_CLEAN) || ((output_context->op & PHP_OUTPUT_HANDLER_START) && !(output_context->op & PHP_OUTPUT_HANDLER_FINAL)))) {
 			size_t len;
-			char *p = strstr(get_output_encoding(), "//");
+			const char *p = strstr(get_output_encoding(), "//");
 
 			if (p) {
 				len = spprintf(&content_type, 0, "Content-Type:%.*s; charset=%.*s", mimetype_len ? mimetype_len : (int) strlen(mimetype), mimetype, (int) (p - get_output_encoding()), get_output_encoding());
@@ -417,16 +418,16 @@ static php_iconv_err_t _php_iconv_appendc(smart_str *d, const char c, iconv_t cd
 
 /* {{{ */
 #ifdef ICONV_BROKEN_IGNORE
-static int _php_check_ignore(const char *charset)
+static bool _php_check_ignore(const char *charset)
 {
 	size_t clen = strlen(charset);
 	if (clen >= 9 && strcmp("//IGNORE", charset+clen-8) == 0) {
-		return 1;
+		return true;
 	}
 	if (clen >= 19 && strcmp("//IGNORE//TRANSLIT", charset+clen-18) == 0) {
-		return 1;
+		return true;
 	}
-	return 0;
+	return false;
 }
 #else
 #define _php_check_ignore(x) (0)
@@ -442,7 +443,7 @@ PHP_ICONV_API php_iconv_err_t php_iconv_string(const char *in_p, size_t in_len,
 	size_t bsz, result = 0;
 	php_iconv_err_t retval = PHP_ICONV_ERR_SUCCESS;
 	zend_string *out_buf;
-	int ignore_ilseq = _php_check_ignore(out_charset);
+	bool ignore_ilseq = _php_check_ignore(out_charset);
 
 	*out = NULL;
 
@@ -559,7 +560,7 @@ static php_iconv_err_t _php_iconv_strlen(size_t *pretval, const char *str, size_
 	size_t out_left;
 
 	size_t cnt;
-	int more;
+	bool more;
 
 	*pretval = (size_t)-1;
 
@@ -636,7 +637,7 @@ static php_iconv_err_t _php_iconv_substr(smart_str *pretval,
 
 	size_t cnt;
 	size_t total_len;
-	int more;
+	bool more;
 
 	err = _php_iconv_strlen(&total_len, str, nbytes, enc);
 	if (err != PHP_ICONV_ERR_SUCCESS) {
@@ -774,8 +775,7 @@ static php_iconv_err_t _php_iconv_strpos(size_t *pretval,
 	size_t ndl_buf_left;
 
 	size_t match_ofs;
-	int more;
-	size_t iconv_ret;
+	bool more;
 
 	*pretval = (size_t)-1;
 
@@ -812,7 +812,7 @@ static php_iconv_err_t _php_iconv_strpos(size_t *pretval,
 
 		more = in_left > 0;
 
-		iconv_ret = iconv(cd, more ? (ICONV_CONST char **)&in_p : NULL, more ? &in_left : NULL, (char **) &out_p, &out_left);
+		size_t iconv_ret = iconv(cd, more ? (ICONV_CONST char **)&in_p : NULL, more ? &in_left : NULL, (char **) &out_p, &out_left);
 		if (out_left == sizeof(buf)) {
 			break;
 		}
@@ -2255,11 +2255,7 @@ PHP_FUNCTION(iconv_set_encoding)
 	retval = zend_alter_ini_entry(name, charset, PHP_INI_USER, PHP_INI_STAGE_RUNTIME);
 	zend_string_release_ex(name, 0);
 
-	if (retval == SUCCESS) {
-		RETURN_TRUE;
-	} else {
-		RETURN_FALSE;
-	}
+	RETURN_BOOL(retval == SUCCESS);
 }
 /* }}} */
 
@@ -2577,7 +2573,7 @@ static php_stream_filter *php_iconv_stream_filter_factory_create(const char *nam
 {
 	php_stream_filter *retval = NULL;
 	php_iconv_stream_filter *inst;
-	char *from_charset = NULL, *to_charset = NULL;
+	const char *from_charset = NULL, *to_charset = NULL;
 	size_t from_charset_len, to_charset_len;
 
 	if ((from_charset = strchr(name, '.')) == NULL) {
diff --git a/ext/iconv/php_iconv.h b/ext/iconv/php_iconv.h
index 7bc1cce0df9f5..fcabdfaf6449e 100644
--- a/ext/iconv/php_iconv.h
+++ b/ext/iconv/php_iconv.h
@@ -67,7 +67,7 @@ ZEND_TSRMLS_CACHE_EXTERN()
 
 /* {{{ typedef enum php_iconv_err_t */
 typedef enum _php_iconv_err_t {
-	PHP_ICONV_ERR_SUCCESS           = SUCCESS,
+	PHP_ICONV_ERR_SUCCESS           = 0,
 	PHP_ICONV_ERR_CONVERTER         = 1,
 	PHP_ICONV_ERR_WRONG_CHARSET     = 2,
 	PHP_ICONV_ERR_TOO_BIG           = 3,