PHP prepared statement dynamic query
Jul 11, 2025 am 12:34 AM
The following steps are required to construct a query dynamically using PHP preprocessing statements: 1. Collect WHERE conditions and parameters through an array, and flexibly construct the query statement based on the actual passed parameters; 2. Keep the WHERE clause dynamically changes when splicing SQL, and prepare the parameters uniformly; 3. When the number of parameters is greater than 0, call bind_param for binding, pay attention to the same order of the type string and the parameter; 4. Always use parameterized queries to prevent injection, field names or table names need to be whitelisted to verify, and LIKE and NULL values ??should also be handled specially to ensure security and accuracy.
Sometimes we need to dynamically build query statements based on different conditions, but we don’t want to sacrifice security and performance. At this time, using PHP's prepared statements (prepared statements) with dynamic splicing of SQL is a good choice.
1. Common scenarios for dynamic query
You may encounter a situation where the filtering conditions from the front end are not fixed, such as the user search may have multiple optional parameters such as name, age, city, etc. At this time, you cannot write SQL dead, and you must construct the WHERE clause based on the actual passed parameters.
For example:
- The user only passed the name, and SQL should be
WHERE name = ? - The name and age are transmitted at the same time, which should be
WHERE name = ? AND age = ? - No parameter is passed, so WHERE is not added
So the question is: How to flexibly add these conditions while using preprocessing statements?
2. Use arrays to collect conditions and parameters
One solution is to use an array to collect WHERE conditions and corresponding binding values. In this way, you can prepare parameters while spelling SQL, and then execute them in a unified manner.
$conditions = [];
$params = [];
$types = '';
if (!empty($_GET['name'])) {
$conditions[] = "name = ?";
$params[] = $_GET['name'];
$types .= 's';
}
if (!empty($_GET['age'])) {
$conditions[] = "age = ?";
$params[] = $_GET['age'];
$types .= 'i';
}
$where_clause = !empty($conditions) ? ' WHERE ' . implode(' AND ', $conditions) : '';
$sql = "SELECT * FROM users" . $where_clause;This allows SQL query statements to be dynamically generated based on the passed parameters and keep the structure clear.
3. Bind parameters and execute query
Next is the standard preprocessing process:
- Preparation statement
- Bind parameters
- Execute a query
If the number of parameters is greater than 0, bind_param will be called:
$stmt = $conn->prepare($sql);
if ($stmt) {
if (!empty($params)) {
$stmt->bind_param($types, ...$params);
}
$stmt->execute();
$result = $stmt->get_result();
// Process the result set...
}Notice:
- The type string
$typesmust correspond to the parameters one by one. - Parameters must be passed in order and cannot be disrupted
- If the
...expand operator is used, the PHP version must support it
4. Tips to prevent injection and syntax errors
- Always use parameterized queries , do not splice variables directly into SQL strings
- Do not splice the field name or table name , unless you do whitelist verification
- The LIKE clause should also be bound with parameters instead of directly spelling
%xxx% - Don't forget to handle NULL values , for example, when allowing null values, you must use
IS NULLto judge
For example:
if ($_GET['city'] === null) {
$conditions[] = "city IS NULL";
} else {
$conditions[] = "city = ?";
$params[] = $_GET['city'];
$types .= 's';
}Basically that's it. After mastering this idea, no matter how the parameters change, you can write safe and flexible query logic.
The above is the detailed content of PHP prepared statement dynamic query. For more information, please follow other related articles on the PHP Chinese website!
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