diff --git a/NEWS b/NEWS
index b3ac9d6b405bf..8f129d715d873 100644
--- a/NEWS
+++ b/NEWS
@@ -263,6 +263,8 @@ PHP                                                                        NEWS
     (nielsdos)
   . Fixed exit code handling of sendmail cmd and added warnings.
     (Jesse Hathaway)
+  . Fixed bug GH-18897 (printf: empty precision is interpreted as precision 6,
+    not as precision 0). (nielsdos)
 
 - Streams:
   . Fixed bug GH-16889 (stream_select() timeout useless for pipes on Windows).
diff --git a/UPGRADING b/UPGRADING
index 1462be95a43fc..4dca8f2b2c213 100644
--- a/UPGRADING
+++ b/UPGRADING
@@ -116,6 +116,11 @@ PHP 8.5 UPGRADE NOTES
   . SplFileObject::fwrite's parameter $length is now nullable. The default
     value changed from 0 to null.
 
+- Standard:
+  . Using a printf-family function with a formatter that did not specify the
+    precision previously incorrectly reset the precision instead of treating
+    it as a precision of 0. See GH-18897.
+
 ========================================
 2. New Features
 ========================================
diff --git a/UPGRADING.INTERNALS b/UPGRADING.INTERNALS
index f421242dba6c6..acc9612b72e30 100644
--- a/UPGRADING.INTERNALS
+++ b/UPGRADING.INTERNALS
@@ -43,6 +43,8 @@ PHP 8.5 INTERNALS UPGRADE NOTES
   . Added the zend_update_exception_properties() function for instantiating
     Exception child classes. It updates the $message, $code, and $previous
     properties.
+  . ZEND_IS_XDIGIT() macro was removed because it was unused and its name
+    did not match its actual behavior.
 
 ========================
 2. Build system changes
diff --git a/Zend/zend_operators.h b/Zend/zend_operators.h
index db86345b69968..a7537d1b3ef33 100644
--- a/Zend/zend_operators.h
+++ b/Zend/zend_operators.h
@@ -156,7 +156,6 @@ static zend_always_inline zend_long zend_dval_to_lval_safe(double d)
 }
 
 #define ZEND_IS_DIGIT(c) ((c) >= '0' && (c) <= '9')
-#define ZEND_IS_XDIGIT(c) (((c) >= 'A' && (c) <= 'F') || ((c) >= 'a' && (c) <= 'f'))
 
 static zend_always_inline uint8_t is_numeric_string_ex(const char *str, size_t length, zend_long *lval,
 	double *dval, bool allow_errors, int *oflow_info, bool *trailing_data)
diff --git a/ext/standard/formatted_print.c b/ext/standard/formatted_print.c
index 9a74ae6c877f3..b2c287c02900c 100644
--- a/ext/standard/formatted_print.c
+++ b/ext/standard/formatted_print.c
@@ -591,6 +591,7 @@ php_formatted_print(char *format, size_t format_len, zval *args, int argc, int n
 						expprec = 1;
 					} else {
 						precision = 0;
+						adjusting |= ADJ_PRECISION;
 					}
 				} else {
 					precision = 0;
diff --git a/ext/standard/tests/strings/gh18897.phpt b/ext/standard/tests/strings/gh18897.phpt
new file mode 100644
index 0000000000000..328ea7161e023
--- /dev/null
+++ b/ext/standard/tests/strings/gh18897.phpt
@@ -0,0 +1,10 @@
+--TEST--
+GH-18897 (printf: empty precision is interpreted as precision 6, not as precision 0)
+--FILE--
+<?php
+printf("%.f\n", 3.1415926535);
+printf("%.0f\n", 3.1415926535);
+?>
+--EXPECT--
+3
+3
diff --git a/main/debug_gdb_scripts.c b/main/debug_gdb_scripts.c
index 3806f6aab60dd..e3c522bc04843 100644
--- a/main/debug_gdb_scripts.c
+++ b/main/debug_gdb_scripts.c
@@ -719,6 +719,8 @@ asm(
     ".ascii \"        for field in self.val.type.fields():\\n\"\n"
     ".ascii \"            if field.name == 'val':\\n\"\n"
     ".ascii \"                yield ('val', format_zstr(self.val))\\n\"\n"
+    ".ascii \"            elif field.name == 'h':\\n\"\n"
+    ".ascii \"                yield (field.name, \\\"0x%x\\\" % self.val[field.name])\\n\"\n"
     ".ascii \"            else:\\n\"\n"
     ".ascii \"                yield (field.name, format_nested(self.val[field.name]))\\n\"\n"
     ".ascii \"\\n\"\n"
@@ -751,12 +753,11 @@ asm(
     ".ascii \"    def children(self):\\n\"\n"
     ".ascii \"        for field in self.val.type.fields():\\n\"\n"
     ".ascii \"            if field.name is None:\\n\"\n"
-    ".ascii \"                name = '<anonymous>'\\n\"\n"
-    ".ascii \"                val = self.val[field]\\n\"\n"
+    ".ascii \"                yield ('<anonymous>', format_nested(self.val[field]))\\n\"\n"
+    ".ascii \"            elif field.name == 'nTableMask':\\n\"\n"
+    ".ascii \"                yield (field.name, \\\"0x%x\\\" % self.val[field.name])\\n\"\n"
     ".ascii \"            else:\\n\"\n"
-    ".ascii \"                name = field.name\\n\"\n"
-    ".ascii \"                val = self.val[field.name]\\n\"\n"
-    ".ascii \"            yield (name, format_nested(val))\\n\"\n"
+    ".ascii \"                yield (field.name, format_nested(self.val[field.name]))\\n\"\n"
     ".ascii \"\\n\"\n"
     ".ascii \"pp_set.add_printer('zend_array', '^_zend_array$', ZendArrayPrettyPrinter)\\n\"\n"
     ".ascii \"\\n\"\n"
diff --git a/scripts/gdb/php_gdb.py b/scripts/gdb/php_gdb.py
index ae8396a2ac0c2..1c5da0154aecd 100644
--- a/scripts/gdb/php_gdb.py
+++ b/scripts/gdb/php_gdb.py
@@ -49,6 +49,8 @@ def children(self):
         for field in self.val.type.fields():
             if field.name == 'val':
                 yield ('val', format_zstr(self.val))
+            elif field.name == 'h':
+                yield (field.name, "0x%x" % self.val[field.name])
             else:
                 yield (field.name, format_nested(self.val[field.name]))
 
@@ -81,12 +83,11 @@ def to_string(self):
     def children(self):
         for field in self.val.type.fields():
             if field.name is None:
-                name = '<anonymous>'
-                val = self.val[field]
+                yield ('<anonymous>', format_nested(self.val[field]))
+            elif field.name == 'nTableMask':
+                yield (field.name, "0x%x" % self.val[field.name])
             else:
-                name = field.name
-                val = self.val[field.name]
-            yield (name, format_nested(val))
+                yield (field.name, format_nested(self.val[field.name]))
 
 pp_set.add_printer('zend_array', '^_zend_array$', ZendArrayPrettyPrinter)