Added: disallow usage of backtick operator

Author: Michal Kral

README.md

@@ -28,6 +28,7 @@
 * Check LSP even for static methods
 * Check missing typehint in anonymous function when a native one could be added
 * Require calling parent constructor
+* Disallow usage of backtick operator (`` $ls = `ls -la` ``)
 
 Additional rules are coming in subsequent releases!
 

src/Rules/DisallowedConstructs/DisallowedBacktickRule.php

@@ -0,0 +1,28 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\DisallowedConstructs;
+
+use PhpParser\Node;
+use PHPStan\Analyser\Scope;
+
+class DisallowedBacktickRule implements \PHPStan\Rules\Rule
+{
+
+	public function getNodeType(): string
+	{
+		return \PhpParser\Node\Expr\ShellExec::class;
+	}
+
+	/**
+	 * @param \PhpParser\Node\Expr\Empty_ $node
+	 * @param \PHPStan\Analyser\Scope $scope
+	 * @return string[]
+	 */
+	public function processNode(Node $node, Scope $scope): array
+	{
+		return [
+			'Backtick operator is not allowed. Use shell_exec() instead.',
+		];
+	}
+
+}

tests/Rules/DisallowedConstructs/DisallowedBacktickRuleTest.php

@@ -0,0 +1,25 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\DisallowedConstructs;
+
+use PHPStan\Rules\Rule;
+
+class DisallowedBacktickRuleTest extends \PHPStan\Testing\RuleTestCase
+{
+
+	protected function getRule(): Rule
+	{
+		return new DisallowedBacktickRule();
+	}
+
+	public function testRule(): void
+	{
+		$this->analyse([__DIR__ . '/data/backtick.php'], [
+			[
+				'Backtick operator is not allowed. Use shell_exec() instead.',
+				3,
+			],
+		]);
+	}
+
+}

tests/Rules/DisallowedConstructs/data/backtick.php

@@ -0,0 +1,3 @@
+<?php
+
+$ls = `ls -la`;