php - If Statement Inside a Function Not working -

similar questions have been posted have not been able find answer.

this if statement works correctly it's self.

$subject_id_top = "case studies"; if($subject_id_top == "case studies") {echo "active";}  

but when inserted if statement inside function not work.

<style>  .active { color:#f00; } </style>   <?php  $subject_id_top = "case studies";  function menu_active() {  if($subject_id_top == "case studies") {echo "active";}  }   <a class="<?php menu_active(); ?>" href="#">case studies</a> ?> 

this seems basic issue life of me havent been able figure out. community great. in advance.

because $subject_id_top inside function refers $subject_id_top outside scope of function (the global scope), have 'import' it, speak, statement:

global $subject_id_top; 

you're function should become:

function menu_active() {     global $subject_id_top;     if($subject_id_top == "case studies") {echo "active";}  } 

however, relying on information outside scopes, in way, not preferable. refactor function accept argument circumvent behavior, so, instance:

function menu_active( $subject_id_top ) {     if($subject_id_top == "case studies") {echo "active";}  } 

and call function $subject_id_top, global scope, argument:

<?php menu_active( $subject_id_top ); ?>