signed userid is already present in table or not. Checked by using PDO and SQL
$no = $dbo->query("select count(userid) from mem_signup where userid='$userid'")->fetchColumn();
if($no >0 ){
$msg=$msg."User Name already exists. Choose a different User Name";
}
Structure of the FORM and Submitting for validation
On submit of this form, all entered variables will be available in form_validate.php page so let us go to form_validate.php page and read the variable and check if any value is there or not. Let us use one flag to check the status of the variables for form validation.
<?php
$userid=$_POST['userid']; // Collect userid using POST method
$password=$_POST['password']; // Collect password using POST method
$flag="OK"; // This is the flag and we set it to OK
$msg=""; // Initializing the message to hold the error messages
if(strlen($userid) < 5){ // must be more than 5 character in length
$msg=$msg."( Please enter user id more than 5 character length )<BR>";
$flag="NOTOK"; //setting the flag to error flag.
}
User id validation is over, now let us start password checking.
if(strlen($password) < 5 ){ // must be more than 5 character in length
$msg=$msg."( Please enter password of more than 5 character length )<BR>";
$flag="NOTOK"; //setting the flag to error flag.
}
Now let us check the flag and give message accordingly, if the flag is set to OK then all validations is
passed and we can proceed for the database checking. If the flag is set to NOTOK
then entries are not ok so we have to display the messages.We also give one back button for the user to go back and correct the
entries.
if($flag <>"OK"){
echo "<center>$msg <br>
<input type='button' value='Retry' onClick='history.go(-1)'></center>";
}else{ // all entries are correct and let us proceed with the database checking etc …
}
This is PHP form validation by using two simple text boxes. We have checked
only the number of characters entered by the user. Now let us move one more step
and go for form validation checking the type of entry. Say in userid fieldother than characters
are not allowed. We will use same flag to set the status and append the message
to the message variable.
if(ctype_alpha($userid)){ //Only lower or upper case letters allowed.
$msg=$msg."( Please use only alphabets a to z as userid )<BR>";
$flag="NOTOK"; //setting the flag to error flag.
}