php代码和html代码语法混合写法，适用于(PHP 4, PHP 5, PHP 7)：

<?php if ($a == 5): ?>
    A is equal to 5
<?php }?>

<?php if ($a == 5){ ?>
    A is equal to 5
<?php } ?>

等价于：

<?php
if ($a == 5):
    echo "A is equal to 5";
endif;
?>

<?php
if ($a == 5){
echo "A is equal to 5";
}
?>