From f838453bf82add5a5dffb0991d6a07fd7cd1a4a0 Mon Sep 17 00:00:00 2001
From: Weilin Du <weilindu@php.net>
Date: Fri, 11 Sep 2026 17:40:58 +0800
Subject: [PATCH 1/2] ext/standard: Optimize str_pad() using doubling copies

---
 UPGRADING                                     |  1 +
 ext/standard/string.c                         | 12 ++++----
 .../strings/str_pad_repeated_pattern.phpt     | 29 +++++++++++++++++++
 3 files changed, 37 insertions(+), 5 deletions(-)
 create mode 100644 ext/standard/tests/strings/str_pad_repeated_pattern.phpt

diff --git a/UPGRADING b/UPGRADING
index 5a5cafc0234f..292ad5fba106 100644
--- a/UPGRADING
+++ b/UPGRADING
@@ -983,6 +983,7 @@ PHP 8.6 UPGRADE NOTES
   . Improved performance of array_walk().
   . Improved performance of intval('+0b...', 2) and intval('0b...', 2).
   . Improved performance of str_split().
+  . Improved performance of str_pad().
 
 - URI:
   . Improved performance of Uri\WhatWg\Url::parse() when collecting
diff --git a/ext/standard/string.c b/ext/standard/string.c
index af3f6a461dcf..0264ff5afee4 100644
--- a/ext/standard/string.c
+++ b/ext/standard/string.c
@@ -5835,13 +5835,15 @@ static void php_str_pad_fill(zend_string *result, size_t pad_chars, const char *
 		return;
 	}
 
+	const char *start = p;
 	const char *end = p + pad_chars;
-	while (p + pad_str_len <= end) {
-		p = zend_mempcpy(p, pad_str, pad_str_len);
-	}
+	size_t len = MIN(pad_str_len, pad_chars);
+	p = zend_mempcpy(p, pad_str, len);
 
-	if (p < end) {
-		memcpy(p, pad_str, end - p);
+	/* Double the filled area on each iteration. */
+	while (p < end) {
+		len = MIN(p - start, end - p);
+		p = zend_mempcpy(p, start, len);
 	}
 
 	ZSTR_LEN(result) += pad_chars;
diff --git a/ext/standard/tests/strings/str_pad_repeated_pattern.phpt b/ext/standard/tests/strings/str_pad_repeated_pattern.phpt
new file mode 100644
index 000000000000..6eebf6d85820
--- /dev/null
+++ b/ext/standard/tests/strings/str_pad_repeated_pattern.phpt
@@ -0,0 +1,29 @@
+--TEST--
+str_pad() with repeated padding patterns and partial final copies
+--FILE--
+<?php
+foreach (['ab', 'abc', "\0\xffab", str_repeat('abc', 11)] as $padding) {
+    foreach (['', 'input'] as $input) {
+        foreach ([0, 1, 2, 3, 4, 5, 7, 8, 9, 15, 16, 17, 31, 32, 33,
+                  63, 64, 65, 255, 256, 257, 1023, 1024, 1025] as $extra) {
+            $repeated = str_repeat($padding, intdiv($extra, strlen($padding)) + 1);
+            $full = substr($repeated, 0, $extra);
+            $left = intdiv($extra, 2);
+            $expected = [
+                STR_PAD_LEFT => $full . $input,
+                STR_PAD_RIGHT => $input . $full,
+                STR_PAD_BOTH => substr($repeated, 0, $left) . $input
+                    . substr($repeated, 0, $extra - $left),
+            ];
+            foreach ($expected as $type => $value) {
+                if (str_pad($input, strlen($input) + $extra, $padding, $type) !== $value) {
+                    throw new Exception("Incorrect padding: type=$type, extra=$extra");
+                }
+            }
+        }
+    }
+}
+echo "Done\n";
+?>
+--EXPECT--
+Done

From 7018c8c4d633ba50f58376605140dc1db76bda73 Mon Sep 17 00:00:00 2001
From: Weilin Du <weilindu@php.net>
Date: Fri, 11 Sep 2026 17:46:54 +0800
Subject: [PATCH 2/2] Remove test

---
 .../strings/str_pad_repeated_pattern.phpt     | 29 -------------------
 1 file changed, 29 deletions(-)
 delete mode 100644 ext/standard/tests/strings/str_pad_repeated_pattern.phpt

diff --git a/ext/standard/tests/strings/str_pad_repeated_pattern.phpt b/ext/standard/tests/strings/str_pad_repeated_pattern.phpt
deleted file mode 100644
index 6eebf6d85820..000000000000
--- a/ext/standard/tests/strings/str_pad_repeated_pattern.phpt
+++ /dev/null
@@ -1,29 +0,0 @@
---TEST--
-str_pad() with repeated padding patterns and partial final copies
---FILE--
-<?php
-foreach (['ab', 'abc', "\0\xffab", str_repeat('abc', 11)] as $padding) {
-    foreach (['', 'input'] as $input) {
-        foreach ([0, 1, 2, 3, 4, 5, 7, 8, 9, 15, 16, 17, 31, 32, 33,
-                  63, 64, 65, 255, 256, 257, 1023, 1024, 1025] as $extra) {
-            $repeated = str_repeat($padding, intdiv($extra, strlen($padding)) + 1);
-            $full = substr($repeated, 0, $extra);
-            $left = intdiv($extra, 2);
-            $expected = [
-                STR_PAD_LEFT => $full . $input,
-                STR_PAD_RIGHT => $input . $full,
-                STR_PAD_BOTH => substr($repeated, 0, $left) . $input
-                    . substr($repeated, 0, $extra - $left),
-            ];
-            foreach ($expected as $type => $value) {
-                if (str_pad($input, strlen($input) + $extra, $padding, $type) !== $value) {
-                    throw new Exception("Incorrect padding: type=$type, extra=$extra");
-                }
-            }
-        }
-    }
-}
-echo "Done\n";
-?>
---EXPECT--
-Done