Endforeach loop different class for first item - php

Question

I'm not that good at php. What i have is a list of items looped with endforeach. What I want is that the first loop will have a class of col-lg-12 and from the second one that class will become col-lg-6. How can I achive that?
Here's the code:
<?php $firstLoop = true;
foreach( $network_value as $key => $value ){
if( $firstLoop ){
echo '<div class="col-lg-12">';
}
echo '<div class="col-lg-6">';
$firstLoop = false;
} ?>
^This is the code that I've tried, but it's not working how i wanted.
<?php if ($img): ?>
<img src="<?php echo $thumb->src ?>" width="<?php echo $thumb->width ?>" height="<?php echo $thumb->height ?>" alt="" />
<?php endif; ?>
<h4>
<div class="circle"><?php echo $datePublic = date('d M', strtotime($page->getCollectionDatePublic())); ?></div>
<br>
<a class="blogTitle" href="<?php echo $url ?>" target="<?php echo $target ?>"><?php echo $title ?></a></h4>
<h6>Posted by <?php echo $author; ?></h6>
<br>
<p><?php echo $description ?></p>
</div>
<?php endforeach; ?>

Answer 1

The most simple way to do it is to add a counter and check if it is the first value in the counter.
<?php
$counter = 0;
foreach( $network_value as $key => $value )
{
if($counter == 0){
echo '<div class="col-lg-12">';
} else {
echo '<div class="col-lg-6">';
}
$counter++;
}
?>
Also I want to add that there are two ways of using foreach and if-statements, but you are trying to mix them, which is wrong.
The first method is using brackets "{" and "}":
foreach($users as $user) {
// do things for each user
echo $user->name; // Example of writing out users name
}
And if-statement:
if(true) {
// do something
}
The second method is using "foreach(statement):" and "endforeach;"
foreach($users as $user):
// do things for each user
echo $user->name; // Example of writing out users name
endforeach;
And if-statement:
if(true):
// do something
endif;

Answer 2

Edited:
In your case you can use:
<?php
foreach ($pages as $key=>$page):
if($key==0){
echo '<div class="col-lg-12">';
} if($key==1){
echo '<div class="col-lg-6">';
}
endforeach; ?>
Or you can use:
<?php
foreach ($pages as $key=>$page):
if($key==0){
echo '<div class="col-lg-12">';
} else {
echo '<div class="col-lg-6">';
}
endforeach; ?>
OLD:
foreach($array as $key=>$row){
if($key==0){
echo '<div class="col-lg-12"></div>';
}
if($key==5){
echo '<div class="col-lg-6"></div>';
}
// OR try use %
if($key%2 == 0){
echo '<div class="col-lg-12"></div>';
} else {
echo '<div class="col-lg-12"></div>';
}