ext/standard/array.c: handle NaN in SORT_REGULAR using totalOrder

Apply IEEE 754 totalOrder predicate for NaN handling in transitive
SORT_REGULAR comparisons. This provides a consistent, deterministic
ordering where NaN values sort after +INF but before non-numeric
strings:

  -INF < finite numbers < +INF < NaN < non-numeric strings

Author: jmarble

ext/standard/array.c

@@ -544,12 +544,24 @@ static int php_array_compare_transitive(zval *op1, zval *op2)
 			return Z_LVAL_P(op1) > Z_LVAL_P(op2) ? 1 : (Z_LVAL_P(op1) < Z_LVAL_P(op2) ? -1 : 0);
 
 		case PHP_ARRAY_TYPE_PAIR(IS_DOUBLE, IS_LONG):
+			if (UNEXPECTED(zend_isnan(Z_DVAL_P(op1)))) {
+				return 1; /* NaN sorts after all integers (totalOrder) */
+			}
 			return ZEND_THREEWAY_COMPARE(Z_DVAL_P(op1), (double) Z_LVAL_P(op2));
 
 		case PHP_ARRAY_TYPE_PAIR(IS_LONG, IS_DOUBLE):
+			if (UNEXPECTED(zend_isnan(Z_DVAL_P(op2)))) {
+				return -1; /* integers sort before NaN (totalOrder) */
+			}
 			return ZEND_THREEWAY_COMPARE((double) Z_LVAL_P(op1), Z_DVAL_P(op2));
 
 		case PHP_ARRAY_TYPE_PAIR(IS_DOUBLE, IS_DOUBLE):
+			if (UNEXPECTED(zend_isnan(Z_DVAL_P(op1)))) {
+				return zend_isnan(Z_DVAL_P(op2)) ? 0 : 1; /* NaN sorts last among doubles (totalOrder) */
+			}
+			if (UNEXPECTED(zend_isnan(Z_DVAL_P(op2)))) {
+				return -1; /* NaN sorts last among doubles (totalOrder) */
+			}
 			return ZEND_THREEWAY_COMPARE(Z_DVAL_P(op1), Z_DVAL_P(op2));
 
 		case PHP_ARRAY_TYPE_PAIR(IS_ARRAY, IS_ARRAY):
@@ -587,17 +599,15 @@ static int php_array_compare_transitive(zval *op1, zval *op2)
 			return -zend_compare_long_to_string_ex(Z_LVAL_P(op2), Z_STR_P(op1), true);
 
 		case PHP_ARRAY_TYPE_PAIR(IS_DOUBLE, IS_STRING):
-			if (zend_isnan(Z_DVAL_P(op1))) {
-				return 1;
+			if (UNEXPECTED(zend_isnan(Z_DVAL_P(op1)))) {
+				return -1; /* NaN sorts before non-numeric strings (totalOrder) */
 			}
-
 			return zend_compare_double_to_string_ex(Z_DVAL_P(op1), Z_STR_P(op2), true);
 
 		case PHP_ARRAY_TYPE_PAIR(IS_STRING, IS_DOUBLE):
-			if (zend_isnan(Z_DVAL_P(op2))) {
-				return 1;
+			if (UNEXPECTED(zend_isnan(Z_DVAL_P(op2)))) {
+				return 1; /* non-numeric strings sort after NaN (totalOrder) */
 			}
-
 			return -zend_compare_double_to_string_ex(Z_DVAL_P(op2), Z_STR_P(op1), true);
 
 		case PHP_ARRAY_TYPE_PAIR(IS_OBJECT, IS_NULL):
@@ -660,6 +670,12 @@ static zend_always_inline int php_array_data_compare_regular_unstable_i(Bucket *
 	}
 
 	if (EXPECTED(Z_TYPE_P(op1) == IS_DOUBLE && Z_TYPE_P(op2) == IS_DOUBLE)) {
+		if (UNEXPECTED(zend_isnan(Z_DVAL_P(op1)))) {
+			return zend_isnan(Z_DVAL_P(op2)) ? 0 : 1; /* NaN sorts last among doubles (totalOrder) */
+		}
+		if (UNEXPECTED(zend_isnan(Z_DVAL_P(op2)))) {
+			return -1; /* NaN sorts last among doubles (totalOrder) */
+		}
 		return ZEND_THREEWAY_COMPARE(Z_DVAL_P(op1), Z_DVAL_P(op2));
 	}
 

ext/standard/tests/array/sort/sort_variation_numeric_strings.phpt

@@ -64,7 +64,17 @@ $a = ["1e2", "1E2", "1e+2", "1e-2", "100"];
 sort($a, SORT_REGULAR);
 var_dump($a);
 
-echo "\n-- Test 13: Consistency check --\n";
+echo "\n-- Test 13: NaN and INF float values (totalOrder) --\n";
+$a = [3.5, NAN, 1, "apple", NAN, 2.0, "10", -INF, INF];
+sort($a, SORT_REGULAR);
+var_dump($a);
+
+echo "\n-- Test 14: NaN and INF float values reversed --\n";
+$a = [3.5, NAN, 1, "apple", NAN, 2.0, "10", -INF, INF];
+rsort($a, SORT_REGULAR);
+var_dump($a);
+
+echo "\n-- Test 15: Consistency check --\n";
 $results = [];
 for ($i = 0; $i < 3; $i++) {
     $a = ["", "0", "00", "A"];
@@ -236,6 +246,50 @@ array(5) {
   string(3) "100"
 }
 
--- Test 13: Consistency check --
+-- Test 13: NaN and INF float values (totalOrder) --
+array(9) {
+  [0]=>
+  float(-INF)
+  [1]=>
+  int(1)
+  [2]=>
+  float(2)
+  [3]=>
+  float(3.5)
+  [4]=>
+  float(INF)
+  [5]=>
+  float(NAN)
+  [6]=>
+  float(NAN)
+  [7]=>
+  string(2) "10"
+  [8]=>
+  string(5) "apple"
+}
+
+-- Test 14: NaN and INF float values reversed --
+array(9) {
+  [0]=>
+  string(5) "apple"
+  [1]=>
+  string(2) "10"
+  [2]=>
+  float(NAN)
+  [3]=>
+  float(NAN)
+  [4]=>
+  float(INF)
+  [5]=>
+  float(3.5)
+  [6]=>
+  float(2)
+  [7]=>
+  int(1)
+  [8]=>
+  float(-INF)
+}
+
+-- Test 15: Consistency check --
 All runs produce same result: yes
 Done