How to execute PHP code in Text Widget without using Plugin

functions.php

/* Sometimes we need to execute PHP scripts in text widget but by default WordPress doesn’t allow this feature because of 
security issues.
Find the functions.php file of your current theme and add the following code at the end of the file.
*/ 

function php_execute($html){
if(strpos($html,"<"."?php")!==false){ ob_start(); eval("?".">".$html);
$html=ob_get_contents();
ob_end_clean();
}
return $html;
}
add_filter('widget_text','php_execute',100);

// use [template_directory_uri] within the sidebar or posts.