MDL-44357 theme: Allow core to compile LESS in PHP

lib/lessphp/Tree/Variable.php

@@ -0,0 +1,51 @@
+<?php
+
+/**
+ * Variable
+ *
+ * @package Less
+ * @subpackage tree
+ */
+class Less_Tree_Variable extends Less_Tree{
+
+	public $name;
+	public $index;
+	public $currentFileInfo;
+	public $evaluating = false;
+	public $type = 'Variable';
+
+    /**
+     * @param string $name
+     */
+    public function __construct($name, $index = null, $currentFileInfo = null) {
+        $this->name = $name;
+        $this->index = $index;
+		$this->currentFileInfo = $currentFileInfo;
+    }
+
+	public function compile($env) {
+
+		if( $this->name[1] === '@' ){
+			$v = new Less_Tree_Variable(substr($this->name, 1), $this->index + 1);
+			$name = '@' . $v->compile($env)->value;
+		}else{
+			$name = $this->name;
+		}
+
+		if ($this->evaluating) {
+			throw new Less_Exception_Compiler("Recursive variable definition for " . $name, null, $this->index, $this->currentFileInfo);
+		}
+
+		$this->evaluating = true;
+
+		foreach($env->frames as $frame){
+			if( $v = $frame->variable($name) ){
+				$this->evaluating = false;
+				return $v->value->compile($env);
+			}
+		}
+
+		throw new Less_Exception_Compiler("variable " . $name . " is undefined", null, $this->index );
+	}
+
+}