[php] allow custom file extensions in frontend

 * add option in frontend to associate custom file extensions to PHP
 * add tests

joern-cli/frontends/php2cpg/src/main/scala/io/joern/php2cpg/Main.scala

@@ -10,6 +10,7 @@ import scopt.OParser
 final case class Config(
   phpIni: Option[String] = None,
   phpParserBin: Option[String] = None,
+  phpExtensions: Set[String] = Set(),
   downloadDependencies: Boolean = false
 ) extends X2CpgConfig[Config]
     with TypeRecoveryParserConfig[Config]
@@ -24,6 +25,10 @@ final case class Config(
     copy(phpParserBin = Some(phpParserBin)).withInheritedFields(this)
   }
 
+  def withExtensions(phpExtensions: Set[String]): Config = {
+    copy(phpExtensions = phpExtensions).withInheritedFields(this)
+  }
+
   override def withDownloadDependencies(downloadDependencies: Boolean): Config = {
     copy(downloadDependencies = downloadDependencies).withInheritedFields(this)
   }

joern-cli/frontends/php2cpg/src/main/scala/io/joern/php2cpg/passes/AstCreationPass.scala

@@ -16,7 +16,7 @@ class AstCreationPass(config: Config, cpg: Cpg, parser: PhpParser)(implicit with
 
   private val logger = LoggerFactory.getLogger(this.getClass)
 
-  val PhpSourceFileExtensions: Set[String] = Set(".php")
+  var PhpSourceFileExtensions: Set[String] = if config.phpExtensions.nonEmpty then config.phpExtensions else Set(".php")
 
   override def generateParts(): Array[String] = SourceFiles
     .determine(

joern-cli/frontends/php2cpg/src/test/scala/io/joern/php2cpg/passes/PhpFileExtensionsTest.scala

@@ -0,0 +1,92 @@
+package io.joern.php2cpg.passes
+
+import io.joern.php2cpg.Config
+import io.joern.php2cpg.parser.Domain.PhpOperators
+import io.joern.php2cpg.testfixtures.PhpCode2CpgFixture
+import io.shiftleft.semanticcpg.language.*
+
+class PhpFileExtensionsTest extends PhpCode2CpgFixture() {
+
+  "two files with two new extensions associated with PHP" should {
+
+    val cpg = code(
+      """
+        |require 'vendor/autoload.php';
+        |
+        |$s3 = new S3Client([
+        |    'version' => 'latest',
+        |    'region'  => 'us-east-1',
+        |    'credentials' => [
+        |        'key'    => 'YOUR_AWS_ACCESS_KEY_ID',
+        |        'secret' => 'YOUR_AWS_SECRET_ACCESS_KEY',
+        |    ]
+        |]);
+        |""".stripMargin,
+      "sample.php"
+    )
+      .moreCode(
+        """<?php
+          |require 'vendor/autoload.php';
+          |
+          |$s3 = new S3Client([
+          |    'version' => 'latest',
+          |    'region'  => 'us-east-1',
+          |    'credentials' => [
+          |        'key'    => 'YOUR_AWS_ACCESS_KEY_ID',
+          |        'secret' => 'YOUR_AWS_SECRET_ACCESS_KEY',
+          |    ]
+          |]);
+          |
+          |""".stripMargin,
+        "something.cls"
+      )
+      .withConfig(Config().withExtensions(Set(".php", ".cls")))
+
+    "be scanned and present in cpg" in {
+      cpg.file.name.l shouldBe List("sample.php", "something.cls", "<unknown>")
+      cpg.file.name.l.size shouldBe 3
+    }
+
+  }
+
+  "two files with only default (.php) extension associated with PHP" should {
+
+    val cpg = code(
+      """
+        |require 'vendor/autoload.php';
+        |
+        |$s3 = new S3Client([
+        |    'version' => 'latest',
+        |    'region'  => 'us-east-1',
+        |    'credentials' => [
+        |        'key'    => 'YOUR_AWS_ACCESS_KEY_ID',
+        |        'secret' => 'YOUR_AWS_SECRET_ACCESS_KEY',
+        |    ]
+        |]);
+        |""".stripMargin,
+      "sample.php"
+    )
+      .moreCode(
+        """<?php
+          |require 'vendor/autoload.php';
+          |
+          |$s3 = new S3Client([
+          |    'version' => 'latest',
+          |    'region'  => 'us-east-1',
+          |    'credentials' => [
+          |        'key'    => 'YOUR_AWS_ACCESS_KEY_ID',
+          |        'secret' => 'YOUR_AWS_SECRET_ACCESS_KEY',
+          |    ]
+          |]);
+          |
+          |""".stripMargin,
+        "something.cls"
+      )
+
+    "be scanned and one default extension present in cpg" in {
+      cpg.file.name.l shouldBe List("sample.php", "<unknown>")
+      cpg.file.name.l.size shouldBe 2
+    }
+  }
+
+}