How can I detect which submit button was pressed?

Question

I have a script in PHP where I need to detect which button was pressed in a HTML page. I have found lots of similar questions asked by other people, but I am having problems.

HTML

<form method="post" action="kode/kode_newsletter_operation.php" id="newsletter_step3Form">
                    <p>
                        <label>Schedule newsletter:</label>
                        <select name="send_date_month" id="send_date_month">
                            <option value="01">January</option>
                            <option value="02">February</option>
                            <option value="03">March</option>
                            <option value="04">April</option>
                            <option value="05">May</option>
                            <option value="06">June</option>
                            <option value="07">July</option>
                            <option value="08">August</option>
                            <option value="09">September</option>
                            <option value="10">October</option>
                            <option value="11">November</option>
                            <option value="12">December</option>
                        </select>
                        -
                        <select name="send_date_day" id="send_date_day">
                            <option value="01">1</option>
                            <option value="02">2</option>
                            <option value="03">3</option>
                            <option value="04">4</option>
                            <option value="05">5</option>
                            <option value="06">6</option>
                            <option value="07">7</option>
                            <option value="08">8</option>
                            <option value="09">9</option>
                            <option value="10">10</option>
                            <option value="11">11</option>
                            <option value="12">12</option>
                            <option value="13">13</option>
                            <option value="14">14</option>
                            <option value="15">15</option>
                            <option value="16">16</option>
                            <option value="17">17</option>
                            <option value="18">18</option>
                            <option value="19">19</option>
                            <option value="20">20</option>
                            <option value="21">21</option>
                            <option value="22">22</option>
                            <option value="23">23</option>
                            <option value="24">24</option>
                            <option value="25">25</option>
                            <option value="26">26</option>
                            <option value="27">27</option>
                            <option value="28">28</option>
                            <option value="29">29</option>
                            <option value="30">30</option>
                            <option value="31">31</option>
                        </select>
                        -
                        <select name="send_date_year" id="send_date_year">
                            <option value='2012'>2012</option><option value='2013'>2013</option>                                </select>&nbsp;
                            <select name="send_date_hour" id="send_date_hour">
                                <option value="00">0</option>
                                <option value="01">1</option>
                                <option value="02">2</option>
                                <option value="03">3</option>
                                <option value="04">4</option>
                                <option value="05">5</option>
                                <option value="06">6</option>
                                <option value="07">7</option>
                                <option value="08">8</option>
                                <option value="09">9</option>
                                <option value="10">10</option>
                                <option value="11">11</option>
                                <option value="12">12</option>
                                <option value="13">13</option>
                                <option value="14">14</option>
                                <option value="15">15</option>
                                <option value="16">16</option>
                                <option value="17">17</option>
                                <option value="18">18</option>
                                <option value="19">19</option>
                                <option value="20">20</option>
                                <option value="21">21</option>
                                <option value="22">22</option>
                                <option value="23">23</option>
                            </select>:<select name="send_date_min" id="send_date_min">
                                <option value="00">00</option>
                                <option value="00">05</option>
                                <option value="10">10</option>
                                <option value="00">15</option>
                                <option value="20">20</option>
                                <option value="00">25</option>
                                <option value="30">30</option>
                                <option value="00">35</option>
                                <option value="40">40</option>
                                <option value="00">45</option>
                                <option value="50">50</option>
                                <option value="00">55</option>
                            </select>
                            <div>Server Time: October 12, 2012 04:54</div>
                        </p>
                        <p>
                            <label for="send_date">Preview in Email:</label>
                            <input type="text" id="preview_email"  value="" name="preview_email" />
                            <input type="button" id="preview_btn" name="preview_btn" class="btn btn_red" onclick="previewSendMail(1)" value="Send Preview"/>
                        </p>
                        <p>&nbsp; </p>
                        <div id="kode_result"></div>
                        <div id="content_buttons">
                            <input type="button" class="btn btn_blue big" name="goback" value="Last Step" onclick="window.location.href='./newsletter_create_step2.php?id=1'" />
                            <input type="submit" name="submit_btn_now" value="Send now!" class=" btn btn_red big"/>
                            <input type="submit" name="submit_btn" value="Schedule" class=" btn btn_green big"/>
                            <input name="action" type="hidden" value="newsletter_step3" />
                            <input type="hidden" name="newsletter_id" id="newsletter_id" value="1"/>
                        </div>
                    </form>

PHP

print_r($_POST);

Output

Array(
[send_date_month] => 10
[send_date_day] => 12
[send_date_year] => 2012
[send_date_hour] => 01
[send_date_min] => 50
[preview_email] =>
[action] => newsletter_step3
[newsletter_id] => 1
)

Both buttons are inside the <form> tag but the $_POST array doesn't include any info about them. What am I doing wrong? Do the most recent browsers send no information about the submit button or am I missing something? I have no skills in javascript to develop a workaround for this, I only know PHP.

Thanks in advance.

Answer 1

Give the submit buttons the same name attribute, but with different values, then you can test against the text that is used on the submit button.

<pre><? print_r($_POST);?></pre>
<form method="post">
<input type="submit" name="button" value="AAA">
<input type="submit" name="button" value="BBB">
</form>

Ouput:

Array
(
    [button] => AAA
)

---

Edit: Actually, I see nothing wrong with your code?

<pre><? print_r($_POST);?></pre>
<form method="post">
<input type="submit" name="submit_btn_now" value="Send now!" class=" btn btn_red big"/>
<input type="submit" name="submit_btn" value="Schedule" class=" btn btn_green big"/>
</form>

Output only clicking one:

Array
(
    [submit_btn_now] => Send now!
)

Answer 2

Do you have JQuery or any other JS libraries running on your form? They tend to take over the submit event and thus the submit doesn't come from the actual submit input. Try it without a js library?

EDIT: Here is a work around:

$('#submit_btn_now').on('click', function() {
    var hiddensubmit=document.createElement('input');
    hiddensubmit.value = this.value;
    hiddensubmit.name = this.name;
    hiddensubmit.setAttribute('hidden','hidden');
    $('#newsletter_step3Form').append(hiddensubmit);
    $('#newsletter_step3Form').submit()
    return false;
});

Answer 3

Set both buttons' name attribute to the same value.
Give each button a different value attribute, like so:

<input type="submit" name="submit" value="Log In">
<input type="submit" name="submit" value="Sign Up">

Then you can use an if statement in your php, like so:

if ($_POST['submit']=="Log In") {}
else {} // ELSE DETECTS THE "Sign Up" BUTTON, OR ANY OTHER BUTTON WITH A DIFFERENT VALUE

I think this pretty much gives you exactly the answer you were looking for: A way to detect which button was pressed using just PHP and no JavaScript.

Answer 4

If you want to use the same value for all buttons (as it is the value that is shown as text) you could use the name attribute as information holder and prefix it. The way to get the value is then:

$information = substr(
  end(
    array_filter(
      array_keys($_REQUEST),
      function ($key) { return substr($key, 0, strlen(PREFIX)) == PREFIX; }
    )
  ),
  strlen(PREFIX)
);