PHP PDOStatement::bindParam Tutorial

last modified April 19, 2025

The PDOStatement::bindParam method binds a PHP variable to a parameter in a prepared SQL statement. This provides secure parameterized queries.

Basic Definition

PDOStatement::bindParam binds a variable to a parameter marker in the SQL statement. The variable is bound by reference and evaluated at execute time.

Syntax: bindParam(string|int $param, mixed &$var, int $type = PDO::PARAM_STR, int $maxLength = null, mixed $driverOptions = null). The method returns true on success or false on failure.

Binding Integer Parameter

This example shows how to bind an integer parameter to a prepared statement.

bind_int.php

<?php

declare(strict_types=1);

try {
    $pdo = new PDO('mysql:host=localhost;dbname=testdb', 'user', 'password');
    $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    
    $stmt = $pdo->prepare('SELECT * FROM users WHERE id = :id');
    $id = 5;
    $stmt->bindParam(':id', $id, PDO::PARAM_INT);
    $stmt->execute();
    
    $user = $stmt->fetch();
    if ($user) {
        echo "User found: {$user['name']}";
    }
} catch (PDOException $e) {
    echo "Error: " . $e->getMessage();
}

This binds an integer parameter to the :id placeholder. PDO::PARAM_INT specifies the parameter type. The variable $id is bound by reference and evaluated when execute() is called.

Binding String Parameter

This demonstrates binding a string parameter to a prepared statement.

bind_string.php

<?php

declare(strict_types=1);

try {
    $pdo = new PDO('mysql:host=localhost;dbname=testdb', 'user', 'password');
    $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    
    $stmt = $pdo->prepare('SELECT * FROM users WHERE name = :name');
    $name = 'John Doe';
    $stmt->bindParam(':name', $name, PDO::PARAM_STR);
    $stmt->execute();
    
    $user = $stmt->fetch();
    if ($user) {
        echo "User found with email: {$user['email']}";
    }
} catch (PDOException $e) {
    echo "Error: " . $e->getMessage();
}

This binds a string parameter to the :name placeholder. PDO::PARAM_STR is the default type for string parameters. The variable $name is bound by reference.

Binding Boolean Parameter

This example shows how to bind a boolean parameter to a prepared statement.

bind_bool.php

<?php

declare(strict_types=1);

try {
    $pdo = new PDO('mysql:host=localhost;dbname=testdb', 'user', 'password');
    $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    
    $stmt = $pdo->prepare('UPDATE settings SET active = :active WHERE user_id = 1');
    $active = true;
    $stmt->bindParam(':active', $active, PDO::PARAM_BOOL);
    $stmt->execute();
    
    echo "Setting updated successfully";
} catch (PDOException $e) {
    echo "Error: " . $e->getMessage();
}

This binds a boolean parameter to the :active placeholder. PDO::PARAM_BOOL ensures proper boolean handling. The variable $active is bound by reference.

Binding NULL Parameter

This demonstrates binding a NULL value to a prepared statement parameter.

bind_null.php

<?php

declare(strict_types=1);

try {
    $pdo = new PDO('mysql:host=localhost;dbname=testdb', 'user', 'password');
    $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    
    $stmt = $pdo->prepare('UPDATE users SET middle_name = :middle WHERE id = 1');
    $middle = null;
    $stmt->bindParam(':middle', $middle, PDO::PARAM_NULL);
    $stmt->execute();
    
    echo "Middle name set to NULL successfully";
} catch (PDOException $e) {
    echo "Error: " . $e->getMessage();
}

This binds a NULL value to the :middle placeholder. PDO::PARAM_NULL explicitly indicates a NULL parameter. The variable $middle is bound by reference.

Binding Large String with Length

This shows how to bind a large string parameter with specified length.

bind_large_string.php

<?php

declare(strict_types=1);

try {
    $pdo = new PDO('mysql:host=localhost;dbname=testdb', 'user', 'password');
    $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    
    $stmt = $pdo->prepare('INSERT INTO articles (title, content) VALUES (?, ?)');
    $title = "New Article";
    $content = str_repeat("This is a long article content. ", 100);
    
    $stmt->bindParam(1, $title, PDO::PARAM_STR);
    $stmt->bindParam(2, $content, PDO::PARAM_STR, strlen($content));
    $stmt->execute();
    
    echo "Article inserted successfully";
} catch (PDOException $e) {
    echo "Error: " . $e->getMessage();
}

This binds a large string parameter with specified length. The fourth parameter sets the maximum length. Positional parameters (?) are used instead of named.

Binding Output Parameter

This demonstrates binding an output parameter for a stored procedure call.

bind_output.php

<?php

declare(strict_types=1);

try {
    $pdo = new PDO('mysql:host=localhost;dbname=testdb', 'user', 'password');
    $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    
    $stmt = $pdo->prepare('CALL get_user_email(:id, :email)');
    $id = 5;
    $email = '';
    
    $stmt->bindParam(':id', $id, PDO::PARAM_INT);
    $stmt->bindParam(':email', $email, PDO::PARAM_STR|PDO::PARAM_INPUT_OUTPUT, 255);
    $stmt->execute();
    
    echo "User email: $email";
} catch (PDOException $e) {
    echo "Error: " . $e->getMessage();
}

This binds an output parameter for a stored procedure. PDO::PARAM_INPUT_OUTPUT indicates the parameter is both input and output. The length is specified.

Binding Multiple Parameters

This example shows binding multiple parameters of different types.

bind_multiple.php

<?php

declare(strict_types=1);

try {
    $pdo = new PDO('mysql:host=localhost;dbname=testdb', 'user', 'password');
    $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    
    $stmt = $pdo->prepare('INSERT INTO products (name, price, in_stock) VALUES (:name, :price, :stock)');
    
    $name = "New Product";
    $price = 19.99;
    $stock = true;
    
    $stmt->bindParam(':name', $name, PDO::PARAM_STR);
    $stmt->bindParam(':price', $price, PDO::PARAM_STR); // Using STR for float
    $stmt->bindParam(':stock', $stock, PDO::PARAM_BOOL);
    $stmt->execute();
    
    echo "Product added successfully";
} catch (PDOException $e) {
    echo "Error: " . $e->getMessage();
}

This binds multiple parameters of different types to a prepared statement. Note that for float values, PDO::PARAM_STR is typically used. All variables are bound by reference.

Best Practices

Always use bindParam for security: Prevents SQL injection.
Specify parameter types: Ensures proper data handling.
Use named parameters: Makes code more readable.
Bind by reference: Variables are evaluated at execute time.
Handle errors: Use try-catch blocks for PDO operations.

Source

PHP bindParam Documentation

This tutorial covered the PDOStatement::bindParam method with practical examples showing different parameter types and use cases.

Author

My name is Jan Bodnar, and I am a passionate programmer with extensive programming experience. I have been writing programming articles since 2007. To date, I have authored over 1,400 articles and 8 e-books. I possess more than ten years of experience in teaching programming.

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