Php Form Validation Tutorial

This contact us form requires four input :
• sender name
• sender email
• message subject
• message body
In button online event put “return checkForm();”
The code snippet below shows the client part of contact form.

function checkForm()
{
var cname, cemail, csubject, cmessage;
with(window.document.msgform)
{
cname = sname;
cemail = email;
csubject = subject;
cmessage = message;
}

if(trim(cname.value) == '')
{
alert('Please enter your name');
cname.focus();
return false;
}
else if(trim(cemail.value) == '')
{
alert('Please enter your email');
cemail.focus();
return false;
}
else if(!isEmail(trim(cemail.value)))
{
alert('Email address is not valid');
cemail.focus();
return false;
}
else if(trim(csubject.value) == '')
{
alert('Please enter message subject');
csubject.focus();
return false;
}
else if(trim(cmessage.value) == '')
{
alert('Please enter your message');
cmessage.focus();
return false;
}
else
{
cname.value = trim(cname.value);
cemail.value = trim(cemail.value);
csubject.value = trim(csubject.value);
cmessage.value = trim(cmessage.value);
return true;
}
}
function trim(str)
{
return str.replace(/^\s+|\s+$/g,'');
}
function isEmail(str)
{
var regex = /^[-_.a-z0-9]+@(([-_a-z0-9]+\.)+(ad|ae|aero|af|ag|
ai|al|am|an|ao|aq|ar|arpa|as|at|au|aw|az|ba|bb|bd|be|bf|bg|
bh|bi|biz|bj|bm|bn|bo|br|bs|bt|bv|bw|by|bz|ca|cc|cd|cf|cg|
ch|ci|ck|cl|cm|cn|co|com|coop|cr|cs|cu|cv|cx|cy|cz|de|dj|dk|
dm|do|dz|ec|edu|ee|eg|eh|er|es|et|eu|fi|fj|fk|fm|fo|fr|ga|gb|
gd|ge|gf|gh|gi|gl|gm|gn|gov|gp|gq|gr|gs|gt|gu|gw|gy|hk|hm|hn|
hr|ht|hu|id|ie|il|in|info|int|io|iq|ir|is|it|jm|jo|jp|ke|kg|
kh|ki|km|kn|kp|kr|kw|ky|kz|la|lb|lc|li|lk|lr|ls|lt|lu|lv|ly|
ma|mc|md|mg|mh|mil|mk|ml|mm|mn|mo|mp|mq|mr|ms|mt|mu|museum|
mv|mw|mx|my|mz|na|name|nc|ne|net|nf|ng|ni|nl|no|np|nr|nt|nu|
nz|om|org|pa|pe|pf|pg|ph|pk|pl|pm|pn|pr|pro|ps|pt|pw|py|qa|
re|ro|ru|rw|sa|sb|sc|sd|se|sg|sh|si|sj|sk|sl|sm|sn|so|sr|st|
su|sv|sy|sz|tc|td|tf|tg|th|tj|tk|tm|tn|to|tp|tr|tt|tv|tw|tz|
ua|ug|uk|um|us|uy|uz|va|vc|ve|vg|vi|vn|vu|wf|ws|ye|yt|yu|za|
zm|zw)|(([0-9][0-9]?|[0-1][0-9][0-9]|[2][0-4][0-9]|[2][5][0-5])\.){3}([0-9][0-9]?|[0-1][0-9][0-9]|[2][0-4][0-9]|[2][5][0-5]))$/i;

return regex.test(str);
}