php mysql query condition oop - php

Question

I was wondering how I could make a general function for SELECT mysql queries from my SelectQuery object in PHP. SelectQuery extends Query, which means it inherits the database connection, a realescape method (which is mysqli_real_escape_string()), and a query method which executes the query. Besides that, it also gets a protected variable called _sql, which is the SQL the query() method passes to the database. And it also gets a protected variable called _table, which contains the (escaped) name of the table it's working on.
My code:
public function select($columns = array('*'), $known = null, $limit = null, $offset = null, $orderby = null, $asc = true) {
if (!is_array($columns)) {
new Error('Parameter is not an array.');
return;
}
$select = '';
foreach($columns as $column) {
$select .= (($select != '')?', ':'') . '`' . $this->realescape($column) . '`';
}
$conditions = '';
if (is_array($known)) {
foreach($known as $column => $value) {
$conditions .= (($conditions != '')?' AND ':'WHERE ') . '`' . $this->realescape($column) . '` = ' . ((is_string($value))?'\'':'') . $this->realescape($value) . ((is_string($value))?'\'':'');
}
}
$domain = '';
if ($limit !== null) {
$domain = 'LIMIT ' . $this->realescape($limit);
if ($offset !== null) {
$domain .= ' OFFSET = ' . $this->realescape($offset);
}
}
$order = '';
if ($orderby !== null) {
$order = 'ORDER BY `' . $this->realescape($orderby) . '` ' . (($asc)?'ASC':'DESC');
}
$this->_sql = 'SELECT ' . $select . ' FROM `' . $this->_table . '`';
if ($conditions != '') {
$this->_sql .= ' ' . $conditions;
}
if ($domain != '') {
$this->_sql .= ' ' . $domain;
}
if ($order != '') {
$this->_sql .= ' ' . $order;
}
return $this->query();
}
The $known variable might be set, if set it should be an array which contains all the 'known' elements of the rows we are selecting.
My question: How can I make this so that conditions such as
age < 18, or date > 5120740154 are easily made?
Also, if you think the way I'm making this work is wrong, please say so.
Thanks in advance

Answer 1

Dynamically build WHERE conditions that can use any operators
Create a $where array that holds your where conditions.
$where = array (
'age <' => 18,
'date >' => 5120740154
);
You can build that into your SQL query using a function like this:
private function buildWhereConditions($where) {
$conditions = 'WHERE 1=1';
/*1=1 is just so you can easily append ANDs */
foreach ($where as $key => $value) {
$conditions .= " AND $key $value ";
}
return $conditions;
}
This will return the where conditions to be appended to your query:
WHERE 1=1 AND age < 18 AND date > 5120740154