<?php

namespace DevCoder;

/**
 * Class QueryBuilder
 */
class QueryBuilder
{
    /**
     * @var array<string>
     */
    private $fields = [];

    /**
     * @var array<string>
     */
    private $conditions = [];

    /**
     * @var array<string>
     */
    private $from = [];

    public function __toString(): string
    {
        $where = $this->conditions === [] ? '' : ' WHERE ' . implode(' AND ', $this->conditions);
        return 'SELECT ' . implode(', ', $this->fields)
            . ' FROM ' . implode(', ', $this->from)
            . $where;
    }

    public function select(string ...$select): self
    {
        $this->fields = $select;
        return $this;
    }

    public function where(string ...$where): self
    {
        foreach ($where as $arg) {
            $this->conditions[] = $arg;
        }
        return $this;
    }

    public function from(string $table, ?string $alias = null): self
    {
        if ($alias === null) {
            $this->from[] = $table;
        } else {
            $this->from[] = "${table} AS ${alias}";
        }
        return $this;
    }
}

$query = (new QueryBuilder())
->select('email', 'first_name', 'last_name')
->from('user');

$pdoStatement = $pdo->prepare($query);
$pdoStatement->execute();

$users = $pdoStatement->fetchAll(\PDO::FETCH_ASSOC);

$query = (new QueryBuilder())
->select('u.email', 'u.first_name', 'u.last_name', 'u.active')
->from('user', 'u')
->where('u.email = :email', 'u.active = :bool');

$pdoStatement = $pdo->prepare($query);
$pdoStatement->execute([
    'email' => 'dev@devcoder.xyz', 
    'bool' => 1
    ]
);

$user = $pdoStatement->fetch(\PDO::FETCH_ASSOC);