From a70b65e7a2b4932b9b05a77714e1807ee7e93966 Mon Sep 17 00:00:00 2001
From: Niels Dossche <7771979+ndossche@users.noreply.github.com>
Date: Fri, 7 Nov 2025 22:55:12 +0100
Subject: [PATCH 1/2] standard: Optimize str_split()
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Three optimizations:
- If the entire string is returned, we don't need to duplicate it.
- Use packed filling logic.
- Use fast construction of strings. This is useful when splitting
  strings on length=1. In that case I get a 6x speedup in the code
  below.

Bench:
```php
$x = str_repeat('A', 100);
for ($i = 0; $i < 1000000; $i++)
    str_split($x, 10);
```

On an i7-4790:
```
Benchmark 1: ./sapi/cli/php x.php
  Time (mean ± σ):     160.1 ms ±   6.4 ms    [User: 157.3 ms, System: 1.8 ms]
  Range (min … max):   155.6 ms … 184.7 ms    18 runs

Benchmark 2: ./sapi/cli/php_old x.php
  Time (mean ± σ):     202.6 ms ±   4.0 ms    [User: 199.1 ms, System: 1.9 ms]
  Range (min … max):   197.4 ms … 209.2 ms    14 runs

Summary
  ./sapi/cli/php x.php  ran
    1.27 ± 0.06 times faster than ./sapi/cli/php_old x.php
```

The performance gain increases with smaller lengths.
---
 ext/standard/string.c | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/ext/standard/string.c b/ext/standard/string.c
index 6fb39c5a6bd2..ddf4221bf6ed 100644
--- a/ext/standard/string.c
+++ b/ext/standard/string.c
@@ -6152,23 +6152,31 @@ PHP_FUNCTION(str_split)
 		}
 
 		array_init_size(return_value, 1);
-		add_next_index_stringl(return_value, ZSTR_VAL(str), ZSTR_LEN(str));
+		GC_TRY_ADDREF(str);
+		add_next_index_str(return_value, str);
 		return;
 	}
 
 	array_init_size(return_value, (uint32_t)(((ZSTR_LEN(str) - 1) / split_length) + 1));
+	zend_hash_real_init_packed(Z_ARRVAL_P(return_value));
 
 	n_reg_segments = ZSTR_LEN(str) / split_length;
 	p = ZSTR_VAL(str);
 
-	while (n_reg_segments-- > 0) {
-		add_next_index_stringl(return_value, p, split_length);
-		p += split_length;
-	}
+	ZEND_HASH_FILL_PACKED(Z_ARRVAL_P(return_value)) {
+		zval zv;
+		while (n_reg_segments-- > 0) {
+			ZEND_ASSERT(split_length > 0);
+			ZVAL_STRINGL_FAST(&zv, p, split_length);
+			ZEND_HASH_FILL_ADD(&zv);
+			p += split_length;
+		}
 
-	if (p != (ZSTR_VAL(str) + ZSTR_LEN(str))) {
-		add_next_index_stringl(return_value, p, (ZSTR_VAL(str) + ZSTR_LEN(str) - p));
-	}
+		if (p != (ZSTR_VAL(str) + ZSTR_LEN(str))) {
+			ZVAL_STRINGL_FAST(&zv, p, (ZSTR_VAL(str) + ZSTR_LEN(str) - p));
+			ZEND_HASH_FILL_ADD(&zv);
+		}
+	} ZEND_HASH_FILL_END();
 }
 /* }}} */
 

From 91a570d78a3fccead0cb0ee97dfa6b7b00aa2976 Mon Sep 17 00:00:00 2001
From: Niels Dossche <7771979+ndossche@users.noreply.github.com>
Date: Sat, 8 Nov 2025 23:01:26 +0100
Subject: [PATCH 2/2] [ci skip] UPGRADING

---
 UPGRADING | 1 +
 1 file changed, 1 insertion(+)

diff --git a/UPGRADING b/UPGRADING
index ddef86c1ae37..5da76d924fbf 100644
--- a/UPGRADING
+++ b/UPGRADING
@@ -128,3 +128,4 @@ PHP 8.6 UPGRADE NOTES
   . Improved performance of array_unshift().
   . Improved performance of array_walk().
   . Improved performance of intval('+0b...', 2) and intval('0b...', 2).
+  . Improved performance of str_split().