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Builds JavaScript that updates the contents of one selector based on another.

Builds JavaScript that updates the contents of one selector based on another.

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<? 
       
        /*  To  simulate  database  connectivity,  I'll  fill  some  arrays        */ 
        $store_id  =  array( "1", "3", "4", "5", "6"); 
        $store_state  =  array( "California", "California", "California", "Nevada", "Utah"); 
        $store_city  =  array( "Los  Angeles",  "San  Francisco",  "Walnut  Creek",  "Las  Vegas",  "Salt  Lake City"); 
        $numStores  =  5; 
        $distinct_states  =  array( "California", "Nevada", "Utah"); 
         
        /*  create  the  javascript  function  the  updates  the  city  list  */ 
        echo  "<SCRIPT  Language=\"JavaScript\">\n"; 

        echo  "function  UpdateCity()\n"; 
        echo  "{\n"; 
         
        /*  clear  the  city  selector  */ 
        echo  "\tvar  City  =  document.choose_store.city.options.length;\n"; 
        echo  "\twhile(City  >  0)\n"; 
        echo  "\t{\n"; 
        echo  "\t\tCity--;\n"; 
        echo  "\t\tdocument.choose_store.city.options[City].text  =  '';\n"; 
        echo  "\t\tdocument.choose_store.city.options[City].value  =  '';\n"; 
        echo  "\t}\n\n"; 
        echo  "\tdocument.choose_store.city.options[0].selected  =  true;\n\n"; 

        /*  figure  out  which  state  is  selected*/ 
        echo  "\tvar  StateSelected  =  0;\n"; 
        echo  "\twhile(document.choose_store.state.options[StateSelected].selected==false)  StateSelected++;\n\n"; 

        $StoreState  =  ""; 
        $CityCount  =  0; 
         
        /*  If  this  weren't  a  demo,  I'd  run  a  query  something  like:  */ 
        /*  select  *  from  store  order  by  State                                            */ 
        /*  But  since  this  is  a  demo,  I'll  just  read  from  an  array    */ 
        $RowCount  =  0; 
        while($RowCount  <  $numStores) 
        { 
                $store_ID  =  $store_id[$RowCount]; 
                $store_State  =  $store_state[$RowCount]; 
                $store_City  =  $store_city[$RowCount]; 
                 
                if($StoreState  !=  $store_State) 
                { 
                        if($StoreState  !=  "") 
                        { 
                                echo  "\t}\n"; 
                        } 
                                                         
                        echo  "\tif(document.choose_store.state.options[StateSelected].value  ==  '$store_State')\n"; 
                        echo  "\t{\n"; 

                        echo  "\t\tdocument.choose_store.city.options[0].value  =  0;\n"; 
                        echo  "\t\tdocument.choose_store.city.options[0].text  =  'Choose  a  Store  Location';\n\n"; 
                           
                        $StoreState  =  $store_State; 
                        $CityCount=1; 
                } 
                 
                echo  "\t\tdocument.choose_store.city.options[$CityCount].value  =  '$store_ID';\n"; 
                echo  "\t\tdocument.choose_store.city.options[$CityCount].text  =  '$store_City';\n\n"; 
                $CityCount++; 
                $RowCount++; 
        } 

        echo  "\t}\n"; 

        echo  "}\n"; 


        echo  "</SCRIPT>\n\n"; 

        echo  "<CENTER><FORM  NAME=choose_store>"; 

        echo  "<SELECT  NAME=state  onChange=\"UpdateCity();\">\n"; 
        /*  This  is  another  place  I'd  put  a  query:                                        */ 
        /*  select  distinct  State  from  store  order  by  State                      */ 
        echo  "<OPTION  VALUE=0>Choose  a  State"; 
        $RowCount  =  0; 
        while($RowCount  <  count($distinct_states)) 
        { 
                echo  "<OPTION  VALUE=\""; 
                echo  $distinct_states[$RowCount]; 
                echo  "\">"; 
                echo  $distinct_states[$RowCount]; 
                echo  "\n"; 
                $RowCount++; 
        } 
         
        echo  "</SELECT>\n"; 

        /*  Now  we  need  to  know  how  many  cities  are  listed  for  the  state  with  the  most  stores  */ 
        /*  select  count(*)  as  items  from  store  group  by  State  order  by  items  desc  */ 
        $MaxItems  =  3; 
        echo  "<SELECT  NAME=city>\n"; 
        $RowCount  =  0; 
        while($RowCount  <=  $MaxItems) 
        { 
                echo  "<OPTION  VALUE=$RowCount>"; 
                echo  "Choose  a  Store  Location\n"; 
                $RowCount++; 
        }                 
        echo  "</SELECT><BR><BR>\n"; 

        echo  "</FORM></CENTER>"; 
         
        echo  "<SCRIPT  Language=\"JavaScript\">UpdateCity();</SCRIPT>\n"; 

?> 

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