试试下面的例子就明白了逻辑运算符。复制并粘贴下面的内容到test.php文件，并将PHP程序保存在PHP服务器的文档根目录，使用浏览器浏览。
<html>
<head><title>PHP逻辑运算符范例</title><head>
<body>
<?php
$a = 42;
$b = 0;
if( $a && $b ){
echo "TEST1 : Both a and b are true<br/>";
}else{
echo "TEST1 : Either a or b is false<br/>";
}
if( $a and $b ){
echo "TEST2 : Both a and b are true<br/>";
}else{
echo "TEST2 : Either a or b is false<br/>";
}
if( $a || $b ){
echo "TEST3 : Either a or b is true<br/>";
}else{
echo "TEST3 : Both a and b are false<br/>";
}
if( $a or $b ){
echo "TEST4 : Either a or b is true<br/>";
}else{
echo "TEST4 : Both a and b are false<br/>";
}
$a = 10;
$b = 20;
if( $a ){
echo "TEST5 : a is true <br/>";
}else{
echo "TEST5 : a is false<br/>";
}
if( $b ){
echo "TEST6 : b is true <br/>";
}else{
echo "TEST6 : b is false<br/>";
}
if( !$a ){
echo "TEST7 : a is true <br/>";
}else{
echo "TEST7 : a is false<br/>";
}
if( !$b ){
echo "TEST8 : b is true <br/>";
}else{
echo "TEST8 : b is false<br/>";
}
?>
</body>
</html>
这将产生以下结果
TEST1 : Either a or b is false TEST2 : Either a or b is false TEST3 : Either a or b is true TEST4 : Either a or b is true TEST5 : a is true TEST6 : b is true TEST7 : a is false TEST8 : b is false
