Show all data from mysql column by "ALL" word - php

Question

I have listbox just like this
<select id="brand">
<option value="All">All</option>
<option value="Acer">Acer</option>
<option value="Alcatel">Alcatel</option>
</select>
And when i choose "Acer" then it is fine works (also Alcatel). But how can I add "all" option to select all brands to show.I wrote following PHP code.But it is not works.How can I create php code for "All" word
$dbClass = new Database();
$extraQuery = "";
$subcategories = json_decode($_POST['subcategories']);
if (!empty($subcategories)) {
for ($i = 0; $i < sizeof($subcategories); $i++) {
for ($j = 0; $j < sizeof($subcategories[$i]); $j++) {
if ($i == 0 && $j == 0) {
$stmt = $dbClass::Connect()->prepare("SELECT * FROM user_posts WHERE brand=:brand");
$stmt->execute(array(":brand" => $subcategories[$i][$j]));
if ($stmt->rowCount() > 0) {
$first = "brand";
if ($subcategories[$i][$j] === "All") {
$stmt = $dbClass::Connect()->prepare("SELECT * FROM user_posts WHERE $first like '%'");
$stmt->execute();
$first = $stmt;
}
$extraQuery = "WHERE (" . $extraQuery . $first . " = " . "'" . $subcategories[$i][$j] . "'";
}
}
}
}
}
$first mean there has more columns i have and want set them "All" word

Answer 1

You can set all value to nothing :
<select id="brand">
<option value="">All</option>
<option value="Acer">Acer</option>
<option value="Alcatel">Alcatel</option>
</select>
Then you can add a where clause in you query only if brand is not empty :
$sql = 'SELECT * FROM user_posts';
$bind = array();
if(!empty($brand)){
$sql .= ' WHERE brand = :brand';
$bind[':brand'] = $brand;
}
$stmt = $dbClass::Connect()->prepare($sql);
$stmt->execute($bind);
Some tuning will be needed to suit your need