node: support php predefined constants

fixtures/0011-magic-consts.php

@@ -8,6 +8,8 @@ echo __Line__;
 
 echo __DIR__;
 
+echo PHP_INT_MAX . PHP_EOL ; 
+
 echo __NAMESPACE__;
 
 function Foo() {

main.go

@@ -14,6 +14,13 @@ import (
 	"php2go/parseutil"
 )
 
+const (
+	phpVersionMajor = 7
+	phpVersionMinor = 4
+	phpVersionPatch = 0
+	phpVersionExtra = `-php2go`
+)
+
 func ConvertFile(filename string) (string, error) {
 
 	inputFile, err := ioutil.ReadFile(filename)
@@ -27,7 +34,7 @@ func ConvertFile(filename string) (string, error) {
 		importPackages: make(map[string]struct{}),
 	}
 
-	p, err := parser.NewParser([]byte(inputFile), "7.4")
+	p, err := parser.NewParser([]byte(inputFile), fmt.Sprintf("%d.%d", phpVersionMajor, phpVersionMinor))
 	if err != nil {
 		panic(err)
 	}

node.go

@@ -1502,7 +1502,67 @@ func (this *conversionState) convertNoFreeFloating(n_ node.Node) (string, error)
 		return n.VarName.(*node.Identifier).Value, nil
 
 	case *expr.ConstFetch:
-		return this.resolveName(n.Constant)
+		constRef, err := this.resolveName(n.Constant)
+		if err != nil {
+			return "", err
+		}
+
+		// Handle PHP reserved constants
+		// @ref https://www.php.net/manual/en/reserved.constants.php
+
+		if constRef == `PHP_EOL` {
+			// Not 100% accurate, but realistically this works on Windows too nowadays
+			return `"\n"`, nil
+
+		} else if constRef == `PHP_INT_MAX` {
+			// Go has math.MaxInt64 in the Math package, etc
+			// But we don't know if this package will maybe be built on a 32-bit platform
+			// And we are generating plain `int` types, not necessarily int64 everywhere
+
+			// @ref https://stackoverflow.com/a/54421330
+			this.importPackages["math/bits"] = struct{}{}
+			return `((1 << bits.UintSize) / -2 /* INT_MAX */)`, nil
+
+		} else if constRef == `PHP_VERSION` {
+			return quoteGoString(fmt.Sprintf("%d.%d.%d%s", phpVersionMajor, phpVersionMinor, phpVersionPatch, phpVersionExtra)), nil
+
+		} else if constRef == `PHP_MAJOR_VERSION` {
+			return fmt.Sprintf("%d", phpVersionMajor), nil
+
+		} else if constRef == `PHP_MINOR_VERSION` {
+			return fmt.Sprintf("%d", phpVersionMinor), nil
+
+		} else if constRef == `PHP_RELEASE_VERSION` {
+			return fmt.Sprintf("%d", phpVersionPatch), nil
+
+		} else if constRef == `PHP_VERSION_ID` {
+			return fmt.Sprintf("%d%02d%02d", phpVersionMajor, phpVersionMinor, phpVersionPatch), nil
+
+		} else if constRef == `PHP_EXTRA_VERSION` {
+			return quoteGoString(phpVersionExtra), nil
+
+		} else if constRef == `PHP_ZTS` {
+			return "true /* PHP_ZTS */", nil
+
+		} else if constRef == `PHP_DEBUG` {
+			return "false /* PHP_DEBUG */", nil
+
+		} else if constRef == `PHP_MAXPATHLEN` {
+			// Not 100% accurate
+			// Go filesystem functions can transparently handle long paths
+			// PHP on Linux has a max path of 4096 by default
+			// Just use that
+			return "4096 /* MAXPATHLEN */", nil
+
+		} else if constRef == `PHP_OS` || constRef == `PHP_OS_FAMILY` {
+			// Not 100% accurate, but the right idea
+			this.importPackages["runtime"] = struct{}{}
+			return `runtime.GOOS`, nil
+
+		}
+
+		// No const transformation was required
+		return constRef, nil
 
 	case *expr.Array:
 		return this.convertArrayLiteralCommon(n.Items)