Please recommend a smart, elegant way to write these repetitive 'if' statements

I just know I'm doing this in a really bad way:

<?php } elseif ( is_single()) { 

    $url = wp_get_referer();
    $path_parts = pathinfo($url);
    $mycat = $path_parts['filename'];

    if ( $mycat == "animation"  ) {
        $_SESSION["theCategory"] = $mycat;?>
        <a href="<?php bloginfo('home')?>/category/<?php echo $_SESSION["theCategory"];?>"><?php echo $_SESSION["theCategory"];?></a>
<?php } elseif ($mycat == "direction"){     
        $_SESSION["theCategory"] = $mycat;?>
        <a href="<?php bloginfo('home')?>/category/<?php echo $_SESSION["theCategory"];?>"><?php echo $_SESSION["theCategory"];?></a>
<?php } elseif ($mycat == "grading"){   
        $_SESSION["theCategory"] = $mycat;?>
        <a href="<?php bloginfo('home')?>/category/<?php echo $_SESSION["theCategory"];?>"><?php echo $_SESSION["theCategory"];?></a>
<?php } elseif ($mycat == "online"){    
        $_SESSION["theCategory"] = $mycat;?>
        <a href="<?php bloginfo('home')?>/category/<?php echo $_SESSION["theCategory"];?>"><?php echo $_SESSION["theCategory"];?></a>
<?php } elseif ($mycat == "showcase"){  
        $_SESSION["theCategory"] = $mycat;?>
        <a href="<?php bloginfo('home')?>/category/<?php echo $_SESSION["theCategory"];?>"><?php echo $_SESSION["theCategory"];?></a>
<?php } elseif ($mycat == "showreel"){  
        $_SESSION["theCategory"] = $mycat;?>
        <a href="<?php bloginfo('home')?>/category/<?php echo $_SESSION["theCategory"];?>"><?php echo $_SESSION["theCategory"];?></a>
<?php } elseif ($mycat == "vfx"){   
        $_SESSION["theCategory"] = $mycat;?>
        <a href="<?php bloginfo('home')?>/category/<?php echo $_SESSION["theCategory"];?>"><?php echo $_SESSION["theCategory"];?></a>
<?php }else{ ?><a href="<?php bloginfo('home')?>/category/<?php echo $_SESSION["theCategory"];?>"><?php echo $_SESSION["theCategory"];?></a><?php };?>

<?php } //end if is_single ?>

It works. But it's messy and repetitive. I tried going this route:

<?php if ($开发者_如何转开发mycat == "animation" || "direction" || "grading"){

But it didn't work at all.

Create an array holding the values, then test if the value of $mycat exists in the array. Also, you're echoing the link whatever $mycat is, so the else statement can be completely dropped and the if structure further simplified to just the following:

$categories = array(
    'animation', 
    'direction', 
    'grading', 
    'online', 
    'showcase', 
    'showreel', 
    'vfx'
);

if (in_array($mycat, $categories)) {
    $_SESSION["theCategory"] = $mycat;
}

?>
<a href="<?php bloginfo('home')?>/category/<?php echo $_SESSION["theCategory"];?>"><?php echo $_SESSION["theCategory"];?></a>

And like others have said, remember to escape your output.

Something like this?

<?php
$cats = array(
    'animation',
    'direction',
    'grading',
    'online',
    'showcase',
    'showreel'
    'vfx',
);
if ( in_array($mycat, $cats) ) :
    $_SESSION['theCategory'] = $mycat; ?>
    <a href="<?php bloginfo('home')?>/category/<?php echo $mycat;?>"><?php echo $mycat;?></a>
<?php else: ?>
    <a href="<?php bloginfo('home')?>/category/<?php echo $_SESSION["theCategory"];?>"><?php echo $_SESSION["theCategory"];?></a>
<?php endif; ?>

And using the switch statement:

switch($mycat) {
    case 'animation':
    case 'direction':
    case 'grading':
    case 'online':
    case 'showcase':
    case 'showreel':
    case 'vfx':
        $_SESSION["theCategory"] = $mycat; 
    default:
        ?>
        <a href="<?php bloginfo('home')?>/category/<?php echo $_SESSION["theCategory"];?>"><?php echo $_SESSION["theCategory"];?></a>
        <?php
}

Note the fall-through after the case statements. You could either do that, or:

switch($mycat) {
    case 'animation':
    case 'direction':
    case 'grading':
    case 'online':
    case 'showcase':
    case 'showreel':
    case 'vfx':
        $_SESSION["theCategory"] = $mycat; 
}
?>
<a href="<?php bloginfo('home')?>/category/<?php echo $_SESSION["theCategory"];?>"><?php echo $_SESSION["theCategory"];?></a>
<?php

I don't understand why you even need a conditional here. You're not changing anything inside each conditional possibility.

$_SESSION["theCategory"] = $mycat;
<a href="<?php bloginfo('home')?>/category/<?php echo $_SESSION["theCategory"];?>"><?php echo $_SESSION["theCategory"];?></a>

Use the in_array() function to write you condition:

<?php if (in_array($mycat, array("animation", "direction", "grading")))

Path 1:

<?php if ($mycat == "animation" || $mycat == "direction" || $mycat == "grading"){ 

Path 2:

<?php if (in_array($mycat,array("animation","direction","grading"))) {