[RFC] Add clamp function

ext/standard/basic_functions.stub.php

@@ -1606,6 +1606,12 @@ function min(mixed $value, mixed ...$values): mixed {}
  */
 function max(mixed $value, mixed ...$values): mixed {}
 
+/**
+ * @compile-time-eval
+ * @frameless-function {"arity": 3}
+ */
+function clamp(mixed $value, mixed $min, mixed $max): mixed {}
+
 function array_walk(array|object &$array, callable $callback, mixed $arg = UNKNOWN): true {}
 
 function array_walk_recursive(array|object &$array, callable $callback, mixed $arg = UNKNOWN): true {}

ext/standard/math.c

@@ -389,6 +389,60 @@ PHP_FUNCTION(round)
 }
 /* }}} */
 
+#define PHP_CLAMP(zvalue, zmin, zmax) { \
+	if (EXPECTED(Z_TYPE_P(zmin) == IS_DOUBLE) && UNEXPECTED(zend_isnan(Z_DVAL_P(zmin)))) { \
+		zend_argument_value_error(2, "cannot be NAN"); \
+		RETURN_THROWS(); \
+	} \
+ \
+	if (EXPECTED(Z_TYPE_P(zmax) == IS_DOUBLE) && UNEXPECTED(zend_isnan(Z_DVAL_P(zmax)))) { \
+		zend_argument_value_error(3, "cannot be NAN"); \
+		RETURN_THROWS(); \
+	} \
+ \
+	if (zend_compare(zmax, zmin) == -1) { \
+		zend_argument_value_error(2, "must be smaller than or equal to argument #3 ($max)"); \
+		RETURN_THROWS(); \
+	} \
+ \
+	if (zend_compare(zmax, zvalue) == -1) { \
+		RETURN_COPY(zmax); \
+	} \
+ \
+	if (zend_compare(zvalue, zmin) == -1) { \
+		RETURN_COPY(zmin); \
+	} \
+ \
+	RETURN_COPY(zvalue); \
+}
+
+/* {{{ Return the given value if in range of min and max */
+PHP_FUNCTION(clamp)
+{
+	zval *zvalue, *zmin, *zmax;
+
+	ZEND_PARSE_PARAMETERS_START(3, 3)
+		Z_PARAM_ZVAL(zvalue)
+		Z_PARAM_ZVAL(zmin)
+		Z_PARAM_ZVAL(zmax)
+	ZEND_PARSE_PARAMETERS_END();
+
+	PHP_CLAMP(zvalue, zmin, zmax);
+}
+/* }}} */
+
+/* {{{ Return the given value if in range of min and max */
+ZEND_FRAMELESS_FUNCTION(clamp, 3)
+{
+	zval *zvalue, *zmin, *zmax;
+	Z_FLF_PARAM_ZVAL(1, zvalue);
+	Z_FLF_PARAM_ZVAL(2, zmin);
+	Z_FLF_PARAM_ZVAL(3, zmax);
+
+	PHP_CLAMP(zvalue, zmin, zmax);
+}
+/* }}} */
+
 /* {{{ Returns the sine of the number in radians */
 PHP_FUNCTION(sin)
 {

ext/standard/tests/math/clamp.phpt

@@ -0,0 +1,97 @@
+--TEST--
+clamp() tests
+--INI--
+precision=14
+date.timezone = UTC
+--FILE--
+<?php
+
+var_dump(clamp(2, 1, 3));
+var_dump(clamp(0, 1, 3));
+var_dump(clamp(6, 1, 3));
+var_dump(clamp(2, 1.3, 3.4));
+var_dump(clamp(2.5, 1, 3));
+var_dump(clamp(2.5, 1.3, 3.4));
+var_dump(clamp(0, 1.3, 3.4));
+var_dump(clamp(M_PI, -INF, INF));
+var_dump(clamp(NAN, 4, 6));
+var_dump(clamp("a", "c", "g"));
+var_dump(clamp("d", "c", "g"));
+echo clamp('2025-08-01', '2025-08-15', '2025-09-15'), "\n";
+echo clamp('2025-08-20', '2025-08-15', '2025-09-15'), "\n";
+echo clamp(new \DateTimeImmutable('2025-08-01'), new \DateTimeImmutable('2025-08-15'), new \DateTimeImmutable('2025-09-15'))->format('Y-m-d'), "\n";
+echo clamp(new \DateTimeImmutable('2025-08-20'), new \DateTimeImmutable('2025-08-15'), new \DateTimeImmutable('2025-09-15'))->format('Y-m-d'), "\n";
+var_dump(clamp(null, -1, 1));
+var_dump(clamp(null, 1, 3));
+var_dump(clamp(null, -3, -1));
+var_dump(clamp(-9999, null, 10));
+var_dump(clamp(12, null, 10));
+
+$a = new \InvalidArgumentException('a');
+$b = new \RuntimeException('b');
+$c = new \LogicException('c');
+echo clamp($a, $b, $c)::class, "\n";
+echo clamp($b, $a, $c)::class, "\n";
+echo clamp($c, $a, $b)::class, "\n";
+
+try {
+    var_dump(clamp(4, NAN, 6));
+} catch (ValueError $error) {
+    echo $error->getMessage(), "\n";
+}
+
+try {
+    var_dump(clamp(7, 6, NAN));
+} catch (ValueError $error) {
+    echo $error->getMessage(), "\n";
+}
+
+try {
+    var_dump(clamp(1, 3, 2));
+} catch (ValueError $error) {
+    echo $error->getMessage(), "\n";
+}
+
+
+try {
+    var_dump(clamp(-9999, 5, null));
+} catch (ValueError $error) {
+    echo $error->getMessage(), "\n";
+}
+
+try {
+    var_dump(clamp(12, -5, null));
+} catch (ValueError $error) {
+    echo $error->getMessage(), "\n";
+}
+
+?>
+--EXPECT--
+int(2)
+int(1)
+int(3)
+int(2)
+float(2.5)
+float(2.5)
+float(1.3)
+float(3.141592653589793)
+float(NAN)
+string(1) "c"
+string(1) "d"
+2025-08-15
+2025-08-20
+2025-08-15
+2025-08-20
+int(-1)
+int(1)
+int(-3)
+int(-9999)
+int(10)
+InvalidArgumentException
+RuntimeException
+LogicException
+clamp(): Argument #2 ($min) cannot be NAN
+clamp(): Argument #3 ($max) cannot be NAN
+clamp(): Argument #2 ($min) must be smaller than or equal to argument #3 ($max)
+clamp(): Argument #2 ($min) must be smaller than or equal to argument #3 ($max)
+clamp(): Argument #2 ($min) must be smaller than or equal to argument #3 ($max)