[RFC] Add mb_ucfirst and mb_lcfirst functions

NEWS

@@ -45,6 +45,7 @@ Intl:
 
 MBString:
   . Added mb_trim, mb_ltrim and mb_rtrim. (Yuya Hamada)
+  . Added mb_ucfirst and mb_lcfirst. (Yuya Hamada)
 
 Opcache:
   . Added large shared segments support for FreeBSD. (David Carlier)

UPGRADING

@@ -331,6 +331,8 @@ PDO_SQLITE:
 - MBString:
   . Added mb_trim, mb_ltrim and mb_rtrim functions.
     RFC: https://wiki.php.net/rfc/mb_trim
+  . Added mb_ucfirst and mb_lcfirst functions.
+    RFC: https://wiki.php.net/rfc/mb_ucfirst
 
 - Opcache:
   . If JIT is enabled, PHP will now exit with a fatal error on startup in case

ext/mbstring/mbstring.c

@@ -2953,6 +2953,47 @@ PHP_FUNCTION(mb_strtolower)
 	RETURN_STR(mbstring_convert_case(PHP_UNICODE_CASE_LOWER, ZSTR_VAL(str), ZSTR_LEN(str), enc));
 }
 
+static void php_mb_ulcfirst(INTERNAL_FUNCTION_PARAMETERS, php_case_mode mode)
+{
+	zend_string *str, *from_encoding = NULL;
+
+	ZEND_PARSE_PARAMETERS_START(1, 2)
+		Z_PARAM_STR(str)
+		Z_PARAM_OPTIONAL
+		Z_PARAM_STR_OR_NULL(from_encoding)
+	ZEND_PARSE_PARAMETERS_END();
+
+	const mbfl_encoding *enc = php_mb_get_encoding(from_encoding, 2);
+	if (!enc) {
+		RETURN_THROWS();
+	}
+
+	zend_string *first = mb_get_substr(str, 0, 1, enc);
+	zend_string *second = mb_get_substr(str, 1, MBFL_SUBSTR_UNTIL_END, enc);
+	zend_string *head = mbstring_convert_case(mode, ZSTR_VAL(first), ZSTR_LEN(first), enc);
+
+	if (zend_string_equals(first, head)) {
+		RETVAL_STR(zend_string_copy(str));
+	}
+
+	zend_string_release_ex(first, false);
+	zend_string *retval = zend_string_concat2(ZSTR_VAL(head), ZSTR_LEN(head), ZSTR_VAL(second), ZSTR_LEN(second));
+	zend_string_release_ex(head, false);
+	zend_string_release_ex(second, false);
+
+	RETVAL_STR(retval);
+}
+
+PHP_FUNCTION(mb_ucfirst)
+{
+	php_mb_ulcfirst(INTERNAL_FUNCTION_PARAM_PASSTHRU, PHP_UNICODE_CASE_TITLE);
+}
+
+PHP_FUNCTION(mb_lcfirst)
+{
+	php_mb_ulcfirst(INTERNAL_FUNCTION_PARAM_PASSTHRU, PHP_UNICODE_CASE_LOWER);
+}
+
 typedef enum {
 	MB_LTRIM = 1,
 	MB_RTRIM = 2,

ext/mbstring/mbstring.stub.php

@@ -135,6 +135,10 @@ function mb_strtoupper(string $string, ?string $encoding = null): string {}
 /** @refcount 1 */
 function mb_strtolower(string $string, ?string $encoding = null): string {}
 
+function mb_ucfirst(string $string, ?string $encoding = null): string {}
+
+function mb_lcfirst(string $string, ?string $encoding = null): string {}
+
 function mb_trim(string $string, string $characters = " \f\n\r\t\v\x00\u{00A0}\u{1680}\u{2000}\u{2001}\u{2002}\u{2003}\u{2004}\u{2005}\u{2006}\u{2007}\u{2008}\u{2009}\u{200A}\u{2028}\u{2029}\u{202F}\u{205F}\u{3000}\u{0085}\u{180E}", ?string $encoding = null): string {}
 
 function mb_ltrim(string $string, string $characters = " \f\n\r\t\v\x00\u{00A0}\u{1680}\u{2000}\u{2001}\u{2002}\u{2003}\u{2004}\u{2005}\u{2006}\u{2007}\u{2008}\u{2009}\u{200A}\u{2028}\u{2029}\u{202F}\u{205F}\u{3000}\u{0085}\u{180E}", ?string $encoding = null): string {}

ext/mbstring/tests/mb_ucfirst_lcfirst.phpt

@@ -0,0 +1,35 @@
+--TEST--
+mb_ucfirst(), mb_lcfirst functions tests
+--EXTENSIONS--
+mbstring
+--FILE--
+<?php
+mb_internal_encoding("UTF-8");
+echo "== Empty String ==\n";
+var_dump(mb_ucfirst(""));
+var_dump(mb_lcfirst(""));
+echo "== mb_ucfirst ==\n";
+var_dump(mb_ucfirst("ａｂ"));
+var_dump(mb_ucfirst("ＡＢＳ"));
+var_dump(mb_ucfirst("đắt quá!"));
+var_dump(mb_ucfirst("აბგ"));
+var_dump(mb_ucfirst("lj"));
+echo "== mb_lcfirst ==\n";
+var_dump(mb_lcfirst("ＡＢＳ"));
+var_dump(mb_lcfirst("Xin chào"));
+var_dump(mb_lcfirst("Đẹp quá!"));
+?>
+--EXPECT--
+== Empty String ==
+string(0) ""
+string(0) ""
+== mb_ucfirst ==
+string(6) "Ａｂ"
+string(9) "ＡＢＳ"
+string(12) "Đắt quá!"
+string(9) "აბგ"
+string(2) "Lj"
+== mb_lcfirst ==
+string(9) "ａＢＳ"
+string(9) "xin chào"
+string(12) "đẹp quá!"