Textarea locking - php

Question

I have a simple survey form i designed but for some reason one line of code isnt working.
In question 5. If the user selected the radio button YES then they must enter something in the textarea or the form must not be sent.
If no then the textarea should be locked so nothing can be entered.
Here is the code: Thanks for the help ladies and gentleman
5. Are you using other non-franchise service centres?
<br>
*if yes is there any other reason you would do so other than price
<br>
<input type="radio" name="question5"
<?php if (isset($question5) && $question5=="Yes") echo "checked";?>
value="Yes">Yes
<br>
<input type="radio" name="question5"
<?php if (isset($question5) && $question5=="No") echo "checked";?>
value="No">No
<br>
<textarea name="question5" rows="5" cols="40"><?php echo $question5 </textarea>

Answer 1

Option1: hide the textarea
function check5(selectedType){
if (selectedType == 'Yes'){
document.getElementById('5textarea').style.display = 'block';
} else{
document.getElementById('5textarea').style.display = 'none';
}
}
5. Are you using other non-franchise service centres?
<br>
*if yes is there any other reason you would do so other than price
<br>
<input type="radio" name="question5" value="Yes" onclick="check5(this.value)"> Yes
<br>
<input type="radio" name="question5" value="No" onclick="check5(this.value)"> No
<br>
<textarea id="5textarea" name="question5" rows="5" cols="40" style="display:none"></textarea>
Option2: enable/disable the textarea (NOT TESTED):
5. Are you using other non-franchise service centres?
<br>
*if yes is there any other reason you would do so other than price
<br>
<input type="radio" name="question5" value="Yes" onclick="check5(this.value)"> Yes
<br>
<input type="radio" name="question5" value="No" onclick="check5(this.value)"> No
<br>
<textarea id="5textarea" name="question5" rows="5" cols="40" disabled="true"></textarea>
and change the javascript to:
function check5(selectedType){
if (selectedType == 'Yes'){
document.getElementById("5textarea").disabled = false;
} else{
document.getElementById("5textarea").disabled = true;
}
}

Answer 2

You have to do it with javascript since PHP only runs on the server, not in the browser!
In this code, the textarea is disabled if not needed, and if "Yes" is checked and the textarea doesn't contain enough text, an error appears when submitting the form:
// Javascript:
function validate() {
var radioYes = document.getElementById('radioYes');
var textarea = document.getElementById('textarea');
if (radioYes.checked && textarea.value.length < 10) {
alert('Enter at least 10 characters!');
textarea.focus();
return false;
}
}
function toggle(value) {
document.getElementById('textarea').disabled = value;
}
/* CSS: */
* {
font-family: sans-serif;
margin: 4px;
}
<!-- HTML/PHP: -->
<form action="#">
5. Are you using other non-franchise service centres?<br>
*if yes is there any other reason you would do so other than price?<br>
<input type="radio" name="question5" value="Yes" onchange="toggle(this.selected)" id="radioYes">Yes<br>
<input type="radio" name="question5" value="No" onchange="toggle(!this.selected)">No<br>
<textarea id="textarea" name="question5" rows="5" cols="40" disabled></textarea><br>
<input type="submit" value="Send" onclick="return validate()" />
</form>
JSFiddle