diff --git a/Zend/zend.c b/Zend/zend.c
index c07fabcb36f..30b5a8c134c 100644
--- a/Zend/zend.c
+++ b/Zend/zend.c
@@ -910,7 +910,7 @@ static bool php_auto_globals_create_globals(zend_string *name) /* {{{ */
 {
 	/* While we keep registering $GLOBALS as an auto-global, we do not create an
 	 * actual variable for it. Access to it handled specially by the compiler. */
-	return 0;
+	return false;
 }
 /* }}} */
 
diff --git a/Zend/zend_alloc.c b/Zend/zend_alloc.c
index f3dfe0f9df5..1157dc98fa6 100644
--- a/Zend/zend_alloc.c
+++ b/Zend/zend_alloc.c
@@ -2627,7 +2627,7 @@ ZEND_API bool is_zend_mm(void)
 #if ZEND_MM_CUSTOM
 	return !AG(mm_heap)->use_custom_heap;
 #else
-	return 1;
+	return true;
 #endif
 }
 
diff --git a/Zend/zend_ast.c b/Zend/zend_ast.c
index 9cb3c7aae4a..72202f322e0 100644
--- a/Zend/zend_ast.c
+++ b/Zend/zend_ast.c
@@ -1575,9 +1575,9 @@ static ZEND_COLD bool zend_ast_valid_var_char(char ch)
 	    (c < '0' || c > '9') &&
 	    (c < 'A' || c > 'Z') &&
 	    (c < 'a' || c > 'z')) {
-		return 0;
+		return false;
 	}
-	return 1;
+	return true;
 }
 
 static ZEND_COLD bool zend_ast_valid_var_name(const char *s, size_t len)
@@ -1586,13 +1586,13 @@ static ZEND_COLD bool zend_ast_valid_var_name(const char *s, size_t len)
 	size_t i;
 
 	if (len == 0) {
-		return 0;
+		return false;
 	}
 	c = (unsigned char)s[0];
 	if (c != '_' && c < 127 &&
 	    (c < 'A' || c > 'Z') &&
 	    (c < 'a' || c > 'z')) {
-		return 0;
+		return false;
 	}
 	for (i = 1; i < len; i++) {
 		c = (unsigned char)s[i];
@@ -1600,10 +1600,10 @@ static ZEND_COLD bool zend_ast_valid_var_name(const char *s, size_t len)
 		    (c < '0' || c > '9') &&
 		    (c < 'A' || c > 'Z') &&
 		    (c < 'a' || c > 'z')) {
-			return 0;
+			return false;
 		}
 	}
-	return 1;
+	return true;
 }
 
 static ZEND_COLD bool zend_ast_var_needs_braces(char ch)
diff --git a/Zend/zend_closures.c b/Zend/zend_closures.c
index 4a6b5a52188..4c2b85f5d48 100644
--- a/Zend/zend_closures.c
+++ b/Zend/zend_closures.c
@@ -82,7 +82,7 @@ static bool zend_valid_closure_binding(
 	if (newthis) {
 		if (func->common.fn_flags & ZEND_ACC_STATIC) {
 			zend_error(E_WARNING, "Cannot bind an instance to a static closure, this will be an error in PHP 9");
-			return 0;
+			return false;
 		}
 
 		if (is_fake_closure && func->common.scope &&
@@ -92,23 +92,23 @@ static bool zend_valid_closure_binding(
 					ZSTR_VAL(func->common.scope->name),
 					ZSTR_VAL(func->common.function_name),
 					ZSTR_VAL(Z_OBJCE_P(newthis)->name));
-			return 0;
+			return false;
 		}
 	} else if (is_fake_closure && func->common.scope
 			&& !(func->common.fn_flags & ZEND_ACC_STATIC)) {
 		zend_error(E_WARNING, "Cannot unbind $this of method, this will be an error in PHP 9");
-		return 0;
+		return false;
 	} else if (!is_fake_closure && !Z_ISUNDEF(closure->this_ptr)
 			&& (func->common.fn_flags & ZEND_ACC_USES_THIS)) {
 		zend_error(E_WARNING, "Cannot unbind $this of closure using $this, this will be an error in PHP 9");
-		return 0;
+		return false;
 	}
 
 	if (scope && scope != func->common.scope && scope->type == ZEND_INTERNAL_CLASS) {
 		/* rebinding to internal class is not allowed */
 		zend_error(E_WARNING, "Cannot bind closure to scope of internal class %s, this will be an error in PHP 9",
 				ZSTR_VAL(scope->name));
-		return 0;
+		return false;
 	}
 
 	if (is_fake_closure && scope != func->common.scope) {
@@ -117,10 +117,10 @@ static bool zend_valid_closure_binding(
 		} else {
 			zend_error(E_WARNING, "Cannot rebind scope of closure created from method, this will be an error in PHP 9");
 		}
-		return 0;
+		return false;
 	}
 
-	return 1;
+	return true;
 }
 /* }}} */
 
diff --git a/Zend/zend_cpuinfo.c b/Zend/zend_cpuinfo.c
index 6264031ceba..9f8f1354be0 100644
--- a/Zend/zend_cpuinfo.c
+++ b/Zend/zend_cpuinfo.c
@@ -93,21 +93,21 @@ static unsigned get_xcr0_eax(void) {
 static bool is_avx_supported(void) {
 	if (!(cpuinfo.ecx & ZEND_CPU_FEATURE_AVX)) {
 		/* No support for AVX */
-		return 0;
+		return false;
 	}
 	if (!(cpuinfo.ecx & ZEND_CPU_FEATURE_OSXSAVE)) {
 		/* The operating system does not support XSAVE. */
-		return 0;
+		return false;
 	}
 	if ((get_xcr0_eax() & 0x6) != 0x6) {
 		/* XCR0 SSE and AVX bits must be set. */
-		return 0;
+		return false;
 	}
-	return 1;
+	return true;
 }
 #else
 static bool is_avx_supported(void) {
-	return 0;
+	return false;
 }
 #endif
 
diff --git a/Zend/zend_execute.c b/Zend/zend_execute.c
index 5665cc0c3f7..8eff03056c9 100644
--- a/Zend/zend_execute.c
+++ b/Zend/zend_execute.c
@@ -746,36 +746,36 @@ static bool zend_verify_weak_scalar_type_hint(uint32_t type_mask, zval *arg)
 			if (type == IS_LONG) {
 				zend_string_release(Z_STR_P(arg));
 				ZVAL_LONG(arg, lval);
-				return 1;
+				return true;
 			}
 			if (type == IS_DOUBLE) {
 				zend_string_release(Z_STR_P(arg));
 				ZVAL_DOUBLE(arg, dval);
-				return 1;
+				return true;
 			}
 		} else if (zend_parse_arg_long_weak(arg, &lval, 0)) {
 			zval_ptr_dtor(arg);
 			ZVAL_LONG(arg, lval);
-			return 1;
+			return true;
 		} else if (UNEXPECTED(EG(exception))) {
-			return 0;
+			return false;
 		}
 	}
 	if ((type_mask & MAY_BE_DOUBLE) && zend_parse_arg_double_weak(arg, &dval, 0)) {
 		zval_ptr_dtor(arg);
 		ZVAL_DOUBLE(arg, dval);
-		return 1;
+		return true;
 	}
 	if ((type_mask & MAY_BE_STRING) && zend_parse_arg_str_weak(arg, &str, 0)) {
 		/* on success "arg" is converted to IS_STRING */
-		return 1;
+		return true;
 	}
 	if ((type_mask & MAY_BE_BOOL) == MAY_BE_BOOL && zend_parse_arg_bool_weak(arg, &bval, 0)) {
 		zval_ptr_dtor(arg);
 		ZVAL_BOOL(arg, bval);
-		return 1;
+		return true;
 	}
-	return 0;
+	return false;
 }
 
 #if ZEND_DEBUG
@@ -800,18 +800,18 @@ static bool zend_verify_weak_scalar_type_hint_no_sideeffect(uint32_t type_mask,
 	/* Pass (uint32_t)-1 as arg_num to indicate to ZPP not to emit any deprecation notice,
 	 * this is needed because the version with side effects also uses 0 (e.g. for typed properties) */
 	if ((type_mask & MAY_BE_LONG) && zend_parse_arg_long_weak(arg, &lval, (uint32_t)-1)) {
-		return 1;
+		return true;
 	}
 	if ((type_mask & MAY_BE_DOUBLE) && zend_parse_arg_double_weak(arg, &dval, (uint32_t)-1)) {
-		return 1;
+		return true;
 	}
 	if ((type_mask & MAY_BE_STRING) && can_convert_to_string(arg)) {
-		return 1;
+		return true;
 	}
 	if ((type_mask & MAY_BE_BOOL) == MAY_BE_BOOL && zend_parse_arg_bool_weak(arg, &bval, (uint32_t)-1)) {
-		return 1;
+		return true;
 	}
-	return 0;
+	return false;
 }
 #endif
 
diff --git a/Zend/zend_inheritance.c b/Zend/zend_inheritance.c
index 62b55186d6b..aea142a1f5e 100644
--- a/Zend/zend_inheritance.c
+++ b/Zend/zend_inheritance.c
@@ -312,7 +312,7 @@ static zend_class_entry *lookup_class(zend_class_entry *scope, zend_string *name
 /* Instanceof that's safe to use on unlinked classes. */
 static bool unlinked_instanceof(const zend_class_entry *ce1, const zend_class_entry *ce2) {
 	if (ce1 == ce2) {
-		return 1;
+		return true;
 	}
 
 	if (ce1->ce_flags & ZEND_ACC_LINKED) {
@@ -331,7 +331,7 @@ static bool unlinked_instanceof(const zend_class_entry *ce1, const zend_class_en
 		/* It's not sufficient to only check the parent chain itself, as need to do a full
 		 * recursive instanceof in case the parent interfaces haven't been copied yet. */
 		if (parent_ce && unlinked_instanceof(parent_ce, ce2)) {
-			return 1;
+			return true;
 		}
 	}
 
@@ -342,7 +342,7 @@ static bool unlinked_instanceof(const zend_class_entry *ce1, const zend_class_en
 			 * check here, as the parent interfaces might not have been fully copied yet. */
 			for (i = 0; i < ce1->num_interfaces; i++) {
 				if (unlinked_instanceof(ce1->interfaces[i], ce2)) {
-					return 1;
+					return true;
 				}
 			}
 		} else {
@@ -352,19 +352,19 @@ static bool unlinked_instanceof(const zend_class_entry *ce1, const zend_class_en
 					ZEND_FETCH_CLASS_ALLOW_UNLINKED | ZEND_FETCH_CLASS_NO_AUTOLOAD);
 				/* Avoid recursing if class implements itself. */
 				if (ce && ce != ce1 && unlinked_instanceof(ce, ce2)) {
-					return 1;
+					return true;
 				}
 			}
 		}
 	}
 
-	return 0;
+	return false;
 }
 
 static bool zend_type_permits_self(
 		const zend_type type, const zend_class_entry *scope, zend_class_entry *self) {
 	if (ZEND_TYPE_FULL_MASK(type) & MAY_BE_OBJECT) {
-		return 1;
+		return true;
 	}
 
 	/* Any types that may satisfy self must have already been loaded at this point
@@ -376,11 +376,11 @@ static bool zend_type_permits_self(
 			zend_string *name = resolve_class_name(scope, ZEND_TYPE_NAME(*single_type));
 			const zend_class_entry *ce = lookup_class(self, name);
 			if (ce && unlinked_instanceof(self, ce)) {
-				return 1;
+				return true;
 			}
 		}
 	} ZEND_TYPE_FOREACH_END();
-	return 0;
+	return false;
 }
 
 static void track_class_dependency(zend_class_entry *ce, zend_string *class_name)
diff --git a/Zend/zend_multibyte.c b/Zend/zend_multibyte.c
index 9459920b633..bcecd979099 100644
--- a/Zend/zend_multibyte.c
+++ b/Zend/zend_multibyte.c
@@ -35,7 +35,7 @@ static const char *dummy_encoding_name_getter(const zend_encoding *encoding)
 
 static bool dummy_encoding_lexer_compatibility_checker(const zend_encoding *encoding)
 {
-	return 0;
+	return false;
 }
 
 static const zend_encoding *dummy_encoding_detector(const unsigned char *string, size_t length, const zend_encoding **list, size_t list_size)
diff --git a/Zend/zend_opcode.c b/Zend/zend_opcode.c
index f3631104c62..20fca005321 100644
--- a/Zend/zend_opcode.c
+++ b/Zend/zend_opcode.c
@@ -905,14 +905,14 @@ static bool keeps_op1_alive(zend_op *opline) {
 	 || opline->opcode == ZEND_FETCH_LIST_W
 	 || opline->opcode == ZEND_COPY_TMP
 	 || opline->opcode == ZEND_EXT_STMT) {
-		return 1;
+		return true;
 	}
 	ZEND_ASSERT(opline->opcode != ZEND_FE_FETCH_R
 		&& opline->opcode != ZEND_FE_FETCH_RW
 		&& opline->opcode != ZEND_VERIFY_RETURN_TYPE
 		&& opline->opcode != ZEND_BIND_LEXICAL
 		&& opline->opcode != ZEND_ROPE_ADD);
-	return 0;
+	return false;
 }
 
 /* Live ranges must be sorted by increasing start opline */
diff --git a/Zend/zend_weakrefs.c b/Zend/zend_weakrefs.c
index 0c729755ff4..3b698cc02a7 100644
--- a/Zend/zend_weakrefs.c
+++ b/Zend/zend_weakrefs.c
@@ -237,7 +237,7 @@ static zend_object* zend_weakref_new(zend_class_entry *ce) {
 static zend_always_inline bool zend_weakref_find(zend_object *referent, zval *return_value) {
 	void *tagged_ptr = zend_hash_index_find_ptr(&EG(weakrefs), zend_object_to_weakref_key(referent));
 	if (!tagged_ptr) {
-		return 0;
+		return false;
 	}
 
 	void *ptr = ZEND_WEAKREF_GET_PTR(tagged_ptr);
@@ -247,7 +247,7 @@ static zend_always_inline bool zend_weakref_find(zend_object *referent, zval *re
 found_weakref:
 		wr = ptr;
 		RETVAL_OBJ_COPY(&wr->std);
-		return 1;
+		return true;
 	}
 
 	if (tag == ZEND_WEAKREF_TAG_HT) {
@@ -259,7 +259,7 @@ found_weakref:
 		} ZEND_HASH_FOREACH_END();
 	}
 
-	return 0;
+	return false;
 }
 
 static zend_always_inline void zend_weakref_create(zend_object *referent, zval *return_value) {