I was trying to call the click() function, when a value is selected the selectoption.

But I dont see the call going through, I see the javascript function being call and than call goes to apex:function.

In the debug I can see getStageValue() called again on selecting value in selectoption.  Is the selectoption stopping the call?

<apex:page standardController="Opportunity" extensions="LSOpportunityDetailsController">
    
  <script type="text/javascript">
            function getStageValue(id){
                displayFunction(document.getElementById(id).value);   
            }
  </script>  
 
  <apex:form >
      <apex:actionFunction action="{!click}" name="displayFunction"  rerender="pageblock">
                <apex:param name="stageValue" value=""/>
      </apex:actionFunction>
      
      <apex:pageBlock  id="pageblock">
            <apex:outputlabel value="Stage:" />
            <apex:selectList value="{!stage}" multiselect="false" size="1" id="stageValue" onchange="getStageValue('{!$Component.stageValue}')">
                <apex:selectOptions value="{!StageValue}" />
            </apex:selectList>    
            
        </apex:pageBlock>  
  </apex:form>
</apex:page>

------------------------------------

public with sharing class LSOpportunityDetailsController  {



    private final Opportunity opp;
    private final String procName;
    private Id currentPhase;
    String [] stage = new String []{};
    String para {get;set;}
    List<Goal__c> goalList {get;set;}
    private String stageVal;
    
   
    public LSOpportunityDetailsController(ApexPages.StandardController stdController) {

        System.debug('Called LSOpportunityDetailsController CTOR');
        String i = stdController.getId();
        if (i == null) {
            procName =  'No Id';
            this.opp = new Opportunity();
        }
        else {            
            this.opp = [select id, name, ProcessId__c from Opportunity where id = :i];        
            if (opp.ProcessId__c != null) {
                procName = [SELECT Name FROM Sales_Process__c where Id=:opp.ProcessId__c].Name;
                
            }
        }
                  
    }
    
    public LSOpportunityDetailsController(Id oppId) {
        this.opp = [select id, name, ProcessId__c from Opportunity where id = :oppId];
                
        if (opp.ProcessId__c != null) {
            procName = [SELECT Name FROM Sales_Process__c where Id=:opp.ProcessId__c].Name;
        }
    }
    
    public String[] getStage(){
        return stage;
    }
    
    public void setStage(String [] stage){
        this.stage = stage;
    }
    
    public  List<SelectOption> getStageValue(){
        
        
        List<SelectOption> options = new List<SelectOption>();
        List <Phase__c> phaseList = [select Name from Phase__c where Sales_Process__c=:opp.ProcessId__c ];
        
        for(Phase__c phase:phaseList){
                options.add(new SelectOption(phase.Name,phase.Name));
        }
        return options;
        
    }
    
    public PageReference  click(){
        system.debug('Test' + ApexPages.CurrentPage().getParameters().get('stageValue'));
        stageVal = ApexPages.CurrentPage().getParameters().get('stageValue');
        return null;
    }
    

}