diff --git a/common/functions.php b/common/functions.php
index 27720de26..73944655a 100644
--- a/common/functions.php
+++ b/common/functions.php
@@ -280,8 +280,11 @@ function explode_with_escape($delimiter, $str, $limit = 0, $escape_char = '\\')
  */
 function starts_with($needle, $haystack, $case_sensitive = true)
 {
-	if (strlen($needle) > strlen($haystack)) return false;
-	if ($case_sensitive)
+	if (strlen($needle) > strlen($haystack))
+	{
+		return false;
+	}
+	elseif ($case_sensitive)
 	{
 		return !strncmp($needle, $haystack, strlen($needle));
 	}
@@ -301,14 +304,17 @@ function starts_with($needle, $haystack, $case_sensitive = true)
  */
 function ends_with($needle, $haystack, $case_sensitive = true)
 {
-	if (strlen($needle) > strlen($haystack)) return false;
-	if ($case_sensitive)
+	if (strlen($needle) > strlen($haystack))
 	{
-		return (substr($haystack, -strlen($needle)) === $needle);
+		return false;
+	}
+	elseif ($case_sensitive)
+	{
+		return strval($needle) === '' || substr($haystack, -strlen($needle)) === $needle;
 	}
 	else
 	{
-		return (strtolower(substr($haystack, -strlen($needle))) === strtolower($needle));
+		return strval($needle) === '' || strtolower(substr($haystack, -strlen($needle))) === strtolower($needle);
 	}
 }
 
@@ -322,7 +328,18 @@ function ends_with($needle, $haystack, $case_sensitive = true)
  */
 function contains($needle, $haystack, $case_sensitive = true)
 {
-	return $case_sensitive ? (strpos($haystack, $needle) !== false) : (stripos($haystack, $needle) !== false);
+	if (strlen($needle) > strlen($haystack))
+	{
+		return false;
+	}
+	elseif ($case_sensitive)
+	{
+		return (strpos($haystack, $needle) !== false);
+	}
+	else
+	{
+		return (stripos($haystack, $needle) !== false);
+	}
 }
 
 /**
@@ -714,12 +731,9 @@ function is_empty_html_content($str)
 }
 
 /**
- * Check if there is 'is_countable' function (PHP 7.3)
- * If there is no 'is_countable' function, define it to check for Countable objects.
+ * Polyfill for is_countable() in PHP < 7.3
  * 
- * cf. https://wiki.php.net/rfc/is-countable
- * 
- * @param string $str The input string
+ * @param mixed $var
  * @return bool
 **/
 if (!function_exists('is_countable'))
@@ -729,3 +743,48 @@ if (!function_exists('is_countable'))
         return is_array($var) || $var instanceof Countable;
     }
 }
+
+/**
+ * Polyfill for str_starts_with() in PHP < 8.0
+ * 
+ * @param string $haystack
+ * @param string $needle
+ * @return bool
+ */
+if (!function_exists('str_starts_with'))
+{
+	function str_starts_with($haystack, $needle)
+	{
+		return strval($needle) === '' || strncmp($haystack, $needle, strlen($needle)) === 0;
+	}
+}
+
+/**
+ * Polyfill for str_starts_with() in PHP < 8.0
+ * 
+ * @param string $haystack
+ * @param string $needle
+ * @return bool
+ */
+if (!function_exists('str_ends_with'))
+{
+	function str_ends_with($haystack, $needle)
+	{
+		return strval($needle) === '' || @substr_compare($haystack, $needle, -strlen($needle), strlen($needle)) === 0;
+	}
+}
+
+/**
+ * Polyfill for str_starts_with() in PHP < 8.0
+ * 
+ * @param string $haystack
+ * @param string $needle
+ * @return bool
+ */
+if (!function_exists('str_contains'))
+{
+	function str_contains($haystack, $needle)
+	{
+		return strval($needle) === '' || strpos($haystack, $needle) !== false;
+	}
+}
diff --git a/tests/unit/functions/FunctionsTest.php b/tests/unit/functions/FunctionsTest.php
index 22295c06e..e5447ac49 100644
--- a/tests/unit/functions/FunctionsTest.php
+++ b/tests/unit/functions/FunctionsTest.php
@@ -1,5 +1,13 @@
 <?php
 
+class CountableTest implements Countable
+{
+	public function count(): int
+	{
+		return 42;
+	}
+}
+
 class FunctionsTest extends \Codeception\TestCase\Test
 {
 	public function testArrayFunctions()
@@ -74,16 +82,22 @@ class FunctionsTest extends \Codeception\TestCase\Test
 		$this->assertFalse(starts_with('FOO', 'foobar'));
 		$this->assertTrue(starts_with('FOO', 'foobar', false));
 		$this->assertFalse(starts_with('bar', 'foobar'));
+		$this->assertFalse(starts_with('foobar', 'foo'));
+		$this->assertTrue(starts_with('', 'foobar'));
 		
 		$this->assertTrue(ends_with('bar', 'foobar'));
 		$this->assertFalse(ends_with('BAR', 'foobar'));
 		$this->assertTrue(ends_with('BAR', 'foobar', false));
 		$this->assertFalse(ends_with('foo', 'foobar'));
+		$this->assertFalse(ends_with('foobar', 'bar'));
+		$this->assertTrue(ends_with('', 'foobar'));
 		
 		$this->assertTrue(contains('foo', 'foo bar baz rhymix rocks'));
 		$this->assertFalse(contains('barbaz', 'foo bar baz rhymix rocks'));
 		$this->assertTrue(contains('RHYMIX', 'foo bar baz rhymix rocks', false));
 		$this->assertFalse(contains('ROCKS', 'foo bar baz rhymix rocks'));
+		$this->assertFalse(contains('foobar', 'bar'));
+		$this->assertTrue(contains('', 'foobar'));
 	}
 	
 	public function testRangeFunctions()
@@ -188,6 +202,8 @@ class FunctionsTest extends \Codeception\TestCase\Test
 		$this->assertEquals(3, countobj(array('foo' => 1, 'bar' => 2, 'baz' => 3)));
 		$this->assertEquals(3, countobj((object)array('foo' => 1, 'bar' => 2, 'baz' => 3)));
 		$this->assertEquals(1, countobj('foobar'));
+		$this->assertEquals(42, countobj(new CountableTest));
+		$this->assertEquals(0, countobj(new stdClass));
 	}
 	
 	public function testUTF8Functions()
@@ -243,4 +259,31 @@ class FunctionsTest extends \Codeception\TestCase\Test
 		$this->assertFalse(is_empty_html_content('<p><video src="rickroll.webm" /></p>'));
 		$this->assertFalse(is_empty_html_content('<p><object></object></p>'));
 	}
+	
+	public function testPolyfillFunctions()
+	{
+		$this->assertTrue(function_exists('is_countable'));
+		$this->assertTrue(is_countable(['foo', 'bar']));
+		$this->assertFalse(is_countable('hello world'));
+		$this->assertTrue(is_countable(new CountableTest));
+		$this->assertFalse(is_countable(new stdClass));
+		
+		$this->assertTrue(function_exists('str_starts_with'));
+		$this->assertTrue(str_starts_with('foobar', 'foo'));
+		$this->assertFalse(str_starts_with('Foobar', 'FOO'));
+		$this->assertFalse(str_starts_with('', 'bar'));
+		$this->assertTrue(str_starts_with('foobar', ''));
+		
+		$this->assertTrue(function_exists('str_ends_with'));
+		$this->assertTrue(str_ends_with('foobar', 'bar'));
+		$this->assertFalse(str_ends_with('Foobar', 'BAR'));
+		$this->assertFalse(str_ends_with('', 'bar'));
+		$this->assertTrue(str_ends_with('foobar', ''));
+		
+		$this->assertTrue(function_exists('str_contains'));
+		$this->assertTrue(str_contains('foobarbazz', 'bar'));
+		$this->assertFalse(str_contains('foobarbazz', 'BAR'));
+		$this->assertFalse(str_contains('', 'foobar'));
+		$this->assertTrue(str_contains('foobar', ''));
+	}
 }