Create an array from a for

The code has several important errors:

• You can not have a for loop within the definition of a array
• It seems that you want to simulate a ternary operator, but you lack parts (specifically the most important one that would be the assignment)
• Operations in PHP are separated with a semicolon, and not with a comma or nothing.

To solve these problems you should:

• Define the variable $product_min_qty as an empty array
• Create a loop and fill in the variable within that loop
• The two parts of if..else are equal, you could simplify them directly or, if they are going to be different, use a ternary operator to define each part
• As indicated by Genarito in your comment , the condition of the if can be simplified because the second part ( $i+1>$tama ) will always be false for the values of the loop for .

Something like this (I have not tried it and may contain errors):

$prodlang = $wpdb->get_results("SELECT * FROM wp_post WHERE wp_pedmin!=0");
$tama= count($prodlang);
$product_min_qty = array() 

for($i=0;$i<$tama;$i++){
    $product_min_qty[] = ($i+1 == $tama) ?
                         array( 'id' => $prodlang[$i]->ID , 'min' => $prodlang[$i]->wp_pedmin) :
                         array( 'id' => $prodlang[$i]->ID , 'min' => $prodlang[$i]->wp_pedmin);
}

As I put you in a comment that I deleted, I would recommend that while you are developing you use error_reporting(E_ALL); at the beginning of the page to see what errors you have, because it would be of great help to identify and solve problems such as shared code.

No You can do a for within array , since this would generate a syntax error, you can do the following:

$prodlang = $wpdb->get_results("SELECT * FROM wp_post WHERE wp_pedmin != 0");
$tama= count($prodlang);

$product_min_qty = array(); // Inicializas tu array

for($i=0;$i<$tama;$i++){ // Realizas el for 
    if ($i+1==$tama || $i+1>$tama){
        // Haces un push de acuerdo a tus condiciones
        $product_min_qty[] = array( 'id' => $prodlang[$i]->ID , 'min' => $prodlang[$i]->wp_pedmin); 
    } else {
        // Haces un push de acuerdo a tus demás condiciones
        $product_min_qty[] = array( 'id' => $prodlang[$i]->ID , 'min' => $prodlang[$i]->wp_pedmin); 
    }
}

And now to see the result of this you can make a simple:

echo "<pre>";
print_r($product_min_qty);
echo "</pre>";

I'll give you something similar to what you ask with an example

$array = call_user_func(function() use ($variablesaUsar) {
   // aqui pones el for rellenando un array temporal.
   return $arrayRelleno; // devuelves el array temporal y se asignara a tu     array antes creado llamado $array.
});