URLパラメータに基づいて選択フィールドでオプションを自動選択するにはどうすればよいですか？

Question

以下のフォームで、URLパラメータの値に基づいてさまざまなオプションを自動選択する方法を教えてください。

例：http://example.com/?type=%28shirt%2C+tshirt%2C+t-shirt%29&length=25&width=17&expand=yes

 <form name="shirty" method="get"> 
      <select name="type" /> 
      <option value="(shirt, tshirt, t-shirt)">T-Shirt</option> 
      <option value="(hoodie, sweatshirt)">Sweatshirt</option> 
      </select> 

      <select name="length" /> 
      <option value="select">Select a length</option> 
      <option value="14">14 Inches</option> 
      <option value="15">15 Inches</option> 
      <option value="16">16 Inches</option> 
      <option value="17">17 Inches</option> 
      <option value="18">18 Inches</option> 
      <option value="19">19 Inches</option> 
      <option value="20">20 Inches</option> 

      </select> 


      <select name="width" /> 
      <option value="select">Select a Width</option> 
      <option value="14">14 Inches</option>     
      <option value="15">15 Inches</option> 
      <option value="16">16 Inches</option> 
      <option value="17">17 Inches</option> 
      <option value="18">18 Inches</option> 
      <option value="19">19 Inches</option> 
      <option value="20">20 Inches</option> 
      </select> 

      <input type="checkbox" name="expand" value="yes"" checked><small>include ± 1 inch?</small> 

      <input type="submit" name="Submit" value="Search" /> 

     </form> 

Answer 1

はそれを手に入れました。

 <form name="shirty" method="get"> 
      <select name="type" /> 
      <?php //create the select options 
       $options = " 
        <option value=\"(shirt, tshirt, t-shirt)\">T-Shirt</option> 
        <option value=\"(hoodie, sweatshirt)\">Sweatshirt</option>"; 
        $saved = $type; 
       $saved = (!empty($saved))? $saved: false; 
       if ($saved) 
        //if there is a saved data set the option to selected 
        $options = str_replace('value="'.$saved.'"','value="'.$saved.'" selected="selected"',$options); 
       //echo out the options 
       echo $options; ?> 
       ?> 
      </select> 


      <select name="length" /> 
      <?php //create the select options 
       $options = " 
        <option value=\"14\">14 Inches</option> 
        <option value=\"15\">15 Inches</option> 
        <option value=\"16\">16 Inches</option> 
        <option value=\"17\">17 Inches</option> 
        <option value=\"18\">18 Inches</option> 
        <option value=\"19\">19 Inches</option> 
        <option value=\"20\">20 Inches</option>"; 

        $saved = $length; 
       $saved = (!empty($saved))? $saved: false; 
       if ($saved) 
        //if there is a saved data set the option to selected 
        $options = str_replace('value="'.$saved.'"','value="'.$saved.'" selected="selected"',$options); 
       //echo out the options 
       echo $options; ?> 
       ?> 
      </select> 


      <select name="width" /> 
      <?php //create the select options 
       $options = " 
        <option value=\"14\">14 Inches</option> 
        <option value=\"15\">15 Inches</option> 
        <option value=\"16\">16 Inches</option> 
        <option value=\"17\">17 Inches</option> 
        <option value=\"18\">18 Inches</option> 
        <option value=\"19\">19 Inches</option> 
        <option value=\"20\">20 Inches</option>"; 
        $saved = $width; 
       $saved = (!empty($saved))? $saved: false; 
       if ($saved) 
        //if there is a saved data set the option to selected 
        $options = str_replace('value="'.$saved.'"','value="'.$saved.'" selected="selected"',$options); 
       //echo out the options 
       echo $options; ?> 
       ?> 
      </select> 

      <input type="checkbox" name="expand" value="yes"" checked><small>include ± 1 inch?</small> 

      <input type="submit" name="Submit" value="Search" /> 

      </form> 

Answer 2

<?php 
    //This example creates a select element and marks selected option using selected_id in URL 

     $attributesAssocArray = array(
      "id"=>"someId","class"=>"someClass" 
     ); 

     $optionsArray = array(
      0=>"choose...",1=>"one",2=>"two",3=>"three" 
     ); 

     $selectedId = (!empty($_GET['selected_id'])&&(is_numeric($_GET['selected_id'])))? intval($_GET['selected_id']):-1; 

     echo generate_select($attributesAssocArray,$optionsArray,$selectedId); 

     function generate_select($attributesAssocArray=array(),$optionsArray=array(),$selected=-1) 
     { 
      $attributes = generate_attributes($attributesAssocArray); 
      $html = '<select '.$attributes.'>'; 
      foreach ($optionsArray as $value => $name) 
      { 
       $isSelected = $value==$selected ? " selected" : ""; 
       $html.= '<option value="'.$value.'"'.$isSelected.'>'.$name.'</option>'; 
      } 
      $html.='</select>'; 
      return $html; 
     } 

     function generate_attributes($attributesAssocArray) 
     { 
      $attributes=''; 
      foreach ($attributesAssocArray as $name => $value) 
      { 
       $attributes.= $name.'="'.$value.'" '; 
      } 
      return $attributes; 
     } 
?>