Add assignByRef support

src/Data.php

@@ -153,6 +153,62 @@ public function assign($tpl_var, $value = null, $nocache = false, $scope = null)
         return $this;
     }
 
+	/**
+	 * Assigns a Smarty variable by reference
+	 *
+	 * @param string $tpl_var the template variable name
+	 * @param mixed $value the value (by reference) to assign
+	 * @param boolean $nocache if true any output of this variable will be not cached
+	 * @param int $scope one of self::SCOPE_* constants
+	 *
+	 * @return Data current Data (or Smarty or \Smarty\Template) instance for
+	 *                              chaining
+	 */
+	public function assignByRef($tpl_var, &$value, $nocache = false, $scope = null)
+	{
+		switch ($scope ?? $this->getDefaultScope()) {
+			case self::SCOPE_GLOBAL:
+			case self::SCOPE_SMARTY:
+				$this->getSmarty()->assignByRef($tpl_var, $value);
+				break;
+			case self::SCOPE_TPL_ROOT:
+				$ptr = $this;
+				while (isset($ptr->parent) && ($ptr->parent instanceof Template)) {
+					$ptr = $ptr->parent;
+				}
+				$ptr->assignByRef($tpl_var, $value);
+				break;
+			case self::SCOPE_ROOT:
+				$ptr = $this;
+				while (isset($ptr->parent) && !($ptr->parent instanceof Smarty)) {
+					$ptr = $ptr->parent;
+				}
+				$ptr->assignByRef($tpl_var, $value);
+				break;
+			case self::SCOPE_PARENT:
+				if ($this->parent) {
+					$this->parent->assignByRef($tpl_var, $value);
+				} else {
+					// assign local as fallback
+					$this->assignByRef($tpl_var, $value);
+				}
+				break;
+			case self::SCOPE_LOCAL:
+			default:
+				if (isset($this->tpl_vars[$tpl_var])) {
+					$this->tpl_vars[$tpl_var]->setValueByRef($value);
+					if ($nocache) {
+						$this->tpl_vars[$tpl_var]->setNocache(true);
+					}
+				} else {
+					$this->tpl_vars[$tpl_var] = new Variable(null, $nocache);
+					$this->tpl_vars[$tpl_var]->setValueByRef($value);
+				}
+		}
+
+		return $this;
+	}
+
     /**
      * appends values to template variables
      *

src/Variable.php

@@ -31,6 +31,15 @@ public function setValue($value): void {
 		$this->value = $value;
 	}
 
+	/**
+	 * Set value by reference
+	 *
+	 * @param mixed|null $value
+	 */
+	public function setValueByRef(&$value): void {
+		$this->value = &$value;
+	}
+
     /**
      * if true any output of this variable will be not cached
      *

tests/UnitTests/SmartyMethodsTests/AssignByRef/AssignByRefTest.php

@@ -0,0 +1,70 @@
+<?php
+/**
+ * Smarty PHPunit tests assignByRef method
+ */
+
+/**
+ * Class for assignByRef tests
+ */
+class AssignByRefTest extends PHPUnit_Smarty
+{
+	public function setUp(): void
+	{
+		$this->setUpSmarty(__DIR__);
+	}
+
+	public function testInit()
+	{
+		$this->cleanDirs();
+	}
+
+	private $testStr = null;
+	/**
+	 * Test assignByRef for nullable string property
+	 */
+	public function testAssignByRefForNullableStringProperry()
+	{
+		$this->smarty->assignByRef('myVar', $this->testStr);
+		$this->assertEquals(null, $this->smarty->fetch('eval:{$myVar}'));
+		$this->testStr = 'abc';
+		$this->assertEquals('abc', $this->smarty->fetch('eval:{$myVar}'));
+	}
+
+	/**
+	 * Test assignByRef for string
+	 */
+	public function testAssignByRefForString()
+	{
+		$var = 'abc';
+		$this->smarty->assignByRef('myVar', $var);
+		$this->assertEquals('abc', $this->smarty->fetch('eval:{$myVar}'));
+		$var = 'def';
+		$this->assertEquals('def', $this->smarty->fetch('eval:{$myVar}'));
+	}
+
+	/**
+	 * Test assignByRef for array
+	 */
+	public function testAssignByRefForArray()
+	{
+		$var = array(
+			'a' => 'A',
+		);
+		$this->smarty->assignByRef('myVar', $var);
+		$this->assertEquals('{"a":"A"}', $this->smarty->fetch('eval:{$myVar|json_encode}'));
+		$var['b'] = 'B';
+		$this->assertEquals('{"a":"A","b":"B"}', $this->smarty->fetch('eval:{$myVar|json_encode}'));
+	}
+
+	/**
+	 * Test that assignByRef returns this.
+	 */
+	public function testAssignByRefReturnsThis()
+	{
+		$var = 'data';
+		$this->assertEquals(
+			'data',
+			$this->smarty->assignByRef('dummy', $var)->fetch('eval:{$dummy}')
+		);
+	}
+}