diff --git a/ext/standard/string.c b/ext/standard/string.c
index 0aade780856b9..1e0a6de544c47 100644
--- a/ext/standard/string.c
+++ b/ext/standard/string.c
@@ -150,10 +150,12 @@ static char *php_bin2hex(const unsigned char *old, const size_t oldlen, size_t *
  */
 static char *php_hex2bin(const unsigned char *old, const size_t oldlen, size_t *newlen)
 {
-	size_t target_length = oldlen >> 1;
+	size_t target_length = (oldlen + 1) >> 1;
 	register unsigned char *str = (unsigned char *)safe_emalloc(target_length, sizeof(char), 1);
 	size_t i, j;
-	for (i = j = 0; i < target_length; i++) {
+	/* if we have an odd length, point to the end of the string to distinguish the special case */
+	j = oldlen & 1 ? oldlen : 0;
+	for (i = 0; i < target_length; i++) {
 		char c = old[j++];
 		if (c >= '0' && c <= '9') {
 			str[i] = (c - '0') << 4;
@@ -161,6 +163,10 @@ static char *php_hex2bin(const unsigned char *old, const size_t oldlen, size_t *
 			str[i] = (c - 'a' + 10) << 4;
 		} else if (c >= 'A' && c <= 'F') {
 			str[i] = (c - 'A' + 10) << 4;
+		} else if(c == '\0') {
+			/* odd length, put the first 4 bits to 0 and restart at the beginning of the string */
+			str[i] = 0;
+			j= 0;
 		} else {
 			efree(str);
 			return NULL;