Fix GH-15208: segfault on empty class/function name.

sapi/phpdbg/phpdbg_bp.c

@@ -405,6 +405,12 @@ PHPDBG_API void phpdbg_set_breakpoint_symbol(const char *name, size_t name_len)
 {
 	char *lcname;
 
+	if (!name_len) {
+		phpdbg_error("Empty symbol name");
+		phpdbg_reset_breakpoints();
+		return;
+	}
+
 	if (*name == '\\') {
 		name++;
 		name_len--;
@@ -439,11 +445,24 @@ PHPDBG_API void phpdbg_set_breakpoint_method(const char *class_name, const char
 	size_t func_len = strlen(func_name);
 	char *func_lcname, *class_lcname;
 
+	if (!class_len) {
+		phpdbg_error("Empty class name");
+		phpdbg_reset_breakpoints();
+		return;
+	}
+
+	if (!func_len) {
+		phpdbg_error("Empty function name");
+		phpdbg_reset_breakpoints();
+		return;
+	}
+
 	if (*class_name == '\\') {
 		class_name++;
 		class_len--;
 	}
 
+
 	func_lcname = zend_str_tolower_dup(func_name, func_len);
 	class_lcname = zend_str_tolower_dup(class_name, class_len);
 

sapi/phpdbg/tests/gh15208.phpt

@@ -0,0 +1,46 @@
+--TEST--
+GH-15208 (phpdbg segfault on empty class/function names)
+--PHPDBG--
+r
+c
+--FILE--
+<?php
+
+function test($function) {
+    if (str_contains($function, "zend")) {
+        return;
+    }
+    ob_start();
+    try {
+        @$function();
+    } catch (Throwable) {
+    }
+    try {
+        @$function(null);
+    } catch (Throwable) {
+    }
+    try {
+        @$function(null, null);
+    } catch (Throwable) {
+    }
+    ob_end_clean();
+}
+
+foreach (get_defined_functions()["internal"] as $function) {
+    test($function);
+}
+?>
+--EXPECTF--
+[Successful compilation of %s]
+%a
+Notice: ob_end_clean(): Failed to delete buffer. No buffer to delete in %s on line %d
+%A
+%a
+>00009:         @$function();
+ 00010:     } catch (Throwable) {
+ 00011:     }
+prompt> [Cannot set breakpoint in %s, it is not a regular file]
+[Breakpoint #1 added at ::]
+[Breakpoint #2 added at ]
+[Script ended normally]
+ [The stack contains nothing !]