using the assignment operator

Important

Remember to type the double-equals, because if you were to use a single

equals sign you'd be using the assignment operator discussed above. So,

instead of comparing the variable to the designated value, instead, you'd

assign a new value to the variable (an operation which, incidentally,

evaluates as true). This would not only cause the condition always to be

true, but might also change the value in the variable you're checking,

which could cause all sorts of problems.

Getting Started with PHP

Conditions can be more complex than a single comparison for equality. Recall

that we modified welcome1.php to take a first and last name. If we wanted to

display a special message only for a particular person, we'd have to check the

values of both names (welcome6.php):

$firstname = $_REQUEST['firstname'];

$lastname = $_REQUEST['lastname'];

if ( $firstname == 'Kevin' and $lastname == 'Yank' ) {

echo( 'Welcome, oh glorious leader!' );

} else {

echo( "Welcome to my Website, $firstname $lastname!" );

}

This condition will be true if and only if $firstname has a value of Kevin and

$lastname has a value of Yank. The word and in the above condition makes the

whole condition true only if both of the comparisons evaluate to true. Another

such operator is or, which makes the whole condition true if one or both of two

simple conditions are true. If you're more familiar with the JavaScript or C forms

of these operators (&& and || for and and or respectively), they work in PHP as

well.