一部の電子商取引サイトの国、都市、州、および郵便番号を含めたいのですが、次のようにしたいのです。特定の国を選択すると、その特定の国の都市のみがリストされます。都市が選択されると、その都市の州がドロップダウンに表示され、都市が選択されると、その都市の郵便番号がドロップダウンに表示されます。Google で検索しましたが、信頼できるリンクが見つかりません。誰でもリンクや提案を手伝ってくれます。どんな助けでも大歓迎です。私の現在のコードに感謝します：
<form class="clearboth" name="form" action="" method="post" onSubmit="return sign_up(this);">
<input type="hidden" name="action" value="<?php echo $_GET['action']?>" />
<h1>New User: Sign Up</h1>
<ul class="input_field">
<li><label>Username <span>*</span></label>
<input name="username" class="input_textarea" id="username" size="25" req="1" valimessage="Username cannot be blank"
valiclass="required" />
</li>
<li><label>First Name <span>*</span></label>
<input name="first_name" class="input_textarea" id="first_name" size="25" req="1"
valimessage="First name cannot be blank"
valiclass="required" />
</li>
<li><label>Last Name <span>*</span></label>
<input name="last_name" class="input_textarea" id="last_name" size="25" req="1" valimessage="Last name cannot be blank"
valiclass="required" />
</li>
<li><label>Street address <span>*</span></label>
<input name="address1" class="input_textarea" id="address1" size="25" req="1" valimessage="Street Address cannot be blank"
valiclass="required" />
</li>
<li><label>Street address 2</label>
<input name="address2" class="input_textarea" id="address2" size="25" />
</li>
<li><label>City <span>*</span></label>
<input name="city" class="input_textarea" id="city" size="25" req="1" valimessage="City cannot be blank"
valiclass="required" />
</li>
<li><label>Country <span>*</span></label>
<select name="country" class="input_textarea">
<option
value="NA">Please Select</option>
<option>Afghanistan</option>
<option>Albania</option>
<option>Algeria</option>
<option>American Samoa</option>
<option>Andorra</option>
<option>Angola</option>
<option>Anguilla</option>
<option>Antarctica</option>
<option>Antigua and Barbuda</option>
<option>Argentina</option>
<option>Armenia</option>
<option>Aruba</option>
<option>Australia</option>
<option>Austria</option>
<option>Azerbaijan</option>
<option>Bahamas</option>
<option>Bahrain</option>
<option>Bangladesh</option>
<option>Barbados</option>
<option>Belarus</option>
<option>Belgium</option>
<option>Belize</option>
<option>Benin</option>
<option>Bermuda</option>
<option>Bhutan</option>
<option>Bolivia</option>
<option>Bosnia and Herzegowina</option>
<option>Botswana</option>
<option>Bouvet Island</option>
<option>Brazil</option>
<option>British Indian Ocean Territory</option>
<option>Brunei Darussalam</option>
<option>Bulgaria</option>
<option>Burkina Faso</option>
<option>Burundi</option>
<option>Cambodia</option>
<option>Cameroon</option>
<option>Canada</option>
<option>Cape Verde</option>
<option>Cayman Islands</option>
<option>Central African Republic</option>
<option>Chad</option>
<option>Chile</option>
<option>China</option>
<option>Christmas Island</option>
<option>Cocos (Keeling)Islands</option>
<option>Colombia</option>
<option>Comoros</option>
<option>Congo</option>
<option>Cook Islands</option>
<option>Costa Rica</option>
<option>Cote D'Ivoire</option>
<option>Croatia</option>
<option>Cuba</option>
<option>Cyprus</option>
<option>Czech
Republic</option>
<option>Denmark</option>
<option>Djibouti</option>
<option>Dominica</option>
<option>Dominican
Republic</option>
<option>East Timor</option>
<option>Ecuador</option>
<option>Egypt</option>
<option>El Salvador</option>
<option>Equatorial
Guinea</option>
<option>Eritrea</option>
<option>Estonia</option>
<option>Ethiopia</option>
<option>Falkland
Islands (Malvinas)</option>
<option>Faroe
Islands</option>
<option>Fiji</option>
<option>Finland</option>
<option>France</option>
<option>France, Metropolitan</option>
<option>French Guiana</option>
<option>French
Polynesia</option>
<option>French Southern
Territories</option>
<option>Gabon</option>
<option>Gambia</option>
<option>Georgia</option>
<option>Germany</option>
<option>Ghana</option>
<option>Gibraltar</option>
<option>Greece</option>
<option>Greenland</option>
<option>Grenada</option>
<option>Guadeloupe</option>
<option>Guam</option>
<option>Guatemala</option>
<option>Guinea</option>
<option>Guinea-bissau</option>
<option>Guyana</option>
<option>Haiti</option>
<option>Heard and Mc Donald Islands</option>
<option>Honduras</option>
<option>Hong
Kong</option>
<option>Hungary</option>
<option>Iceland</option>
<option>India</option>
<option>Indonesia</option>
<option>Iran (Islamic
Republic of)</option>
<option>Iraq</option>
<option>Ireland</option>
<option>Israel</option>
<option>Italy</option>
<option>Jamaica</option>
<option>Japan</option>
<option>Jordan</option>
<option>Kazakhstan</option>
<option>Kenya</option>
<option>Kiribati</option>
<option>Korea, Democratic People's Republic
of</option>
<option>Korea, Republic of</option>
<option>Kuwait</option>
<option>Kyrgyzstan</option>
<option>Lao People's
Democratic Republic</option>
<option>Latvia</option>
<option>Lebanon</option>
<option>Lesotho</option>
<option>Liberia</option>
<option>Libyan Arab
Jamahiriya</option>
<option>Liechtenstein</option>
<option>Lithuania</option>
<option>Luxembourg</option>
<option>Macau</option>
<option>Macedonia, The
Former Yugoslav Republic of</option>
<option>Madagascar</option>
<option>Malawi</option>
<option>Malaysia</option>
<option>Maldives</option>
<option>Mali</option>
<option>Malta</option>
<option>Marshall
Islands</option>
<option>Martinique</option>
<option>Mauritania</option>
<option>Mauritius</option>
<option>Mayotte</option>
<option>Mexico</option>
<option>Micronesia, Federated States of</option>
<option>Moldova, Republic of</option>
<option>Monaco</option>
<option>Mongolia</option>
<option>Montserrat</option>
<option>Morocco</option>
<option>Mozambique</option>
<option>Myanmar</option>
<option>Namibia</option>
<option>Nauru</option>
<option>Nepal</option>
<option>Netherlands</option>
<option>Netherlands
Antilles</option>
<option>New Caledonia</option>
<option>New Zealand</option>
<option>Nicaragua</option>
<option>Niger</option>
<option>Nigeria</option>
<option>Niue</option>
<option>Norfolk
Island</option>
<option>Northern Mariana
Islands</option>
<option>Norway</option>
<option>Oman</option>
<option>Pakistan</option>
<option>Palau</option>
<option>Panama</option>
<option>Papua New Guinea</option>
<option>Paraguay</option>
<option>Peru</option>
<option>Philippines</option>
<option>Pitcairn</option>
<option>Poland</option>
<option>Portugal</option>
<option>Puerto
Rico</option>
<option>Qatar</option>
<option>Reunion</option>
<option>Romania</option>
<option>Russian
Federation</option>
<option>Rwanda</option>
<option>Saint Kitts and Nevis</option>
<option>Saint Lucia</option>
<option>Saint
Vincent and the Grenadines</option>
<option>Samoa</option>
<option>San
Marino</option>
<option>Sao Tome and
Principe</option>
<option>Saudi Arabia</option>
<option>Senegal</option>
<option>Seychelles</option>
<option>Sierra
Leone</option>
<option>Singapore</option>
<option>Slovakia (Slovak Republic)</option>
<option>Slovenia</option>
<option>Solomon
Islands</option>
<option>Somalia</option>
<option>South Africa</option>
<option>South
Georgia and the South Sandwich Islands</option>
<option>Spain</option>
<option>Sri
Lanka</option>
<option>St. Helena</option>
<option>St. Pierre and Miquelon</option>
<option>Sudan</option>
<option>Suriname</option>
<option>Svalbard and Jan Mayen Islands</option>
<option>Swaziland</option>
<option>Sweden</option>
<option>Switzerland</option>
<option>Syrian Arab
Republic</option>
<option>Taiwan, Province of
China</option>
<option>Tajikistan</option>
<option>Tanzania, United Republic of</option>
<option>Thailand</option>
<option>Togo</option>
<option>Tokelau</option>
<option>Tonga</option>
<option>Trinidad and Tobago</option>
<option>Tunisia</option>
<option>Turkey</option>
<option>Turkmenistan</option>
<option>Turks and
Caicos Islands</option>
<option>Tuvalu</option>
<option>Uganda</option>
<option>Ukraine</option>
<option>United Arab Emirates</option>
<option>United Kingdom</option>
<option
selected="selected">United States</option>
<option>United
States Minor Outlying Islands</option>
<option>Uruguay</option>
<option>Uzbekistan</option>
<option>Vanuatu</option>
<option>Vatican City
State (Holy See)</option>
<option>Venezuela</option>
<option>Viet
Nam</option>
<option>Virgin Islands
(British)</option>
<option>Virgin Islands
(U.S.)</option>
<option>Wallis and Futuna
Islands</option>
<option>Western Sahara</option>
<option>Yemen</option>
<option>Yugoslavia</option>
<option>Zaire</option>
<option>Zambia</option>
<option>Zimbabwe</option>
</select>
</li>
<li><label>State <span>*</span></label>
<select name="us_state" class="input_textarea">
<option value="NA"
selected="selected">Please Select</option>
<option>Alabama</option>
<option>Alaska</option>
<option>American Samoa</option>
<option>Arizona</option>
<option>Arkansas</option>
<option>Armed Forces
Africa</option>
<option>Armed Forces
Americas</option>
<option>Armed Forces
Canada</option>
<option>Armed Forces
Europe</option>
<option>Armed Forces Middle
East</option>
<option>Armed Forces
Pacific</option>
<option>California</option>
<option>Colorado</option>
<option>Connecticut</option>
<option>Delaware</option>
<option>District of
Columbia</option>
<option>Federated States Of
Micronesia</option>
<option>Florida</option>
<option>Georgia</option>
<option>Guam</option>
<option>Hawaii</option>
<option>Idaho</option>
<option>Illinois</option>
<option>Indiana</option>
<option>Iowa</option>
<option>Kansas</option>
<option>Kentucky</option>
<option>Louisiana</option>
<option>Maine</option>
<option>Marshall
Islands</option>
<option>Maryland</option>
<option>Massachusetts</option>
<option>Michigan</option>
<option>Minnesota</option>
<option>Mississippi</option>
<option>Missouri</option>
<option>Montana</option>
<option>Nebraska</option>
<option>Nevada</option>
<option>New
Hampshire</option>
<option>New Jersey</option>
<option>New Mexico</option>
<option>New
York</option>
<option>North Carolina</option>
<option>North Dakota</option>
<option>Northern
Mariana Islands</option>
<option>Ohio</option>
<option>Oklahoma</option>
<option>Oregon</option>
<option>Palau</option>
<option>Pennsylvania</option>
<option>Puerto
Rico</option>
<option>Rhode Island</option>
<option>South Carolina</option>
<option>South
Dakota</option>
<option>Tenessee</option>
<option>Texas</option>
<option>Utah</option>
<option>Vermont</option>
<option>Virgin
Islands</option>
<option>Virginia</option>
<option>Washington</option>
<option>West
Virginia</option>
<option>Wisconsin</option>
<option>Wyoming</option>
</select>
</li>
<li><label>Zip Code <span>*</span></label>
<input name="zip" class="input_textarea" id="zip" size="25" req="1"
valimessage="Invalid Zip code"
valiclass="zip" />
</li>
<li><label>Phone</label>
<input name="phone" class="input_textarea" id="phone" size="25" />
</li>
<li><label>Fax</label>
<input name="fax" class="input_textarea" id="fax" size="25" />
</li>
<li><label>Email address<span>*</span></label>
<input name="email" class="input_textarea" id="email" size="25" req="1"
valimessage="Invalid email address"
valiclass="email" />
</li>
<li><label>Password <span>*</span></label>
<input name="password" type="password" class="input_textarea" id="password" size="25" req="4"
valimessage="not sufficent password lenghth"
valiclass="required" />
</li>
<li><label>Verify Password</label>
<input name="password2" type="password" class="input_textarea" id="password2" size="25" />
</li>
<li><label> </label>* indicates required fields.</li>
<li><label> </label>
<input type="submit" value="Sign up" name="btn_signup" class="red_btn"/>
</li>
</ul>