Fix: Call to a member function prepare() on bool error in PHP - Quick Solutions

The ‘Call to a member function prepare() on bool’ error occurs when trying to call prepare() on a boolean value instead of a PDO object. This happens when PDO connection fails and returns false.

---

Common Causes and Fixes

1. Failed PDO Connection

<?php
// ❌ Error: Connection failed, $pdo is false
$pdo = new PDO("mysql:host=localhost;dbname=nonexistent", "user", "pass");
$stmt = $pdo->prepare("SELECT * FROM users");  // Error!
?>

<?php
// ✅ Fixed: Check connection success
$pdo = new PDO("mysql:host=localhost;dbname=existing", "user", "pass");
if ($pdo) {
    $stmt = $pdo->prepare("SELECT * FROM users");
}
?>

2. No Error Checking

<?php
// ❌ Error: No error handling
$pdo = new PDO("mysql:host=localhost;dbname=db", "wronguser", "wrongpass");
$stmt = $pdo->prepare("SELECT * FROM users");  // Error!
?>

<?php
// ✅ Fixed: Check connection
$pdo = new PDO("mysql:host=localhost;dbname=db", "user", "pass");
if ($pdo instanceof PDO) {
    $stmt = $pdo->prepare("SELECT * FROM users");
}
?>

3. Exception Mode

<?php
// ❌ Error: Silent failure
$pdo = new PDO("mysql:host=localhost;dbname=db", "user", "pass");
$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_SILENT);
$stmt = $pdo->prepare("SELECT * FROM users");  // May fail silently
?>

<?php
// ✅ Fixed: Exception mode
$pdo = new PDO("mysql:host=localhost;dbname=db", "user", "pass");
$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$stmt = $pdo->prepare("SELECT * FROM users");
?>

4. Using mysql_connect (Wrong Function)

<?php
// ❌ Error: Wrong function, returns bool
$connection = mysql_connect("localhost", "user", "pass");
$stmt = $connection->prepare("SELECT * FROM users");  // Error!
?>

<?php
// ✅ Fixed: Use PDO
$pdo = new PDO("mysql:host=localhost;dbname=db", "user", "pass");
$stmt = $pdo->prepare("SELECT * FROM users");
?>

5. Conditional Assignment

<?php
// ❌ Error: Conditional returns false
$pdo = some_function_that_returns_false();
$stmt = $pdo->prepare("SELECT * FROM users");  // Error!
?>

<?php
// ✅ Fixed: Verify return value
$result = some_function();
$pdo = $result instanceof PDO ? $result : new PDO("dsn", "user", "pass");
$stmt = $pdo->prepare("SELECT * FROM users");
?>

6. Error Suppression

<?php
// ❌ Error: @ suppresses error but returns false
$pdo = @new PDO("mysql:host=localhost;dbname=nonexistent", "user", "pass");
$stmt = $pdo->prepare("SELECT * FROM users");  // Error!
?>

<?php
// ✅ Fixed: No error suppression
$pdo = new PDO("mysql:host=localhost;dbname=existing", "user", "pass");
$stmt = $pdo->prepare("SELECT * FROM users");
?>

7. Function Returning Connection

<?php
// ❌ Error: Function returns false
function getConnection() {
    return false;  // Failed connection
}
$pdo = getConnection();
$stmt = $pdo->prepare("SELECT * FROM users");  // Error!
?>

<?php
// ✅ Fixed: Function returns valid PDO
function getConnection() {
    return new PDO("mysql:host=localhost;dbname=db", "user", "pass");
}
$pdo = getConnection();
$stmt = $pdo->prepare("SELECT * FROM users");
?>

8. Proper Error Handling

<?php
// ❌ Error: No validation
$pdo = new PDO("mysql:host=localhost;dbname=db", "user", "pass");
if ($pdo) {  // This will be true even if connection failed
    $stmt = $pdo->prepare("SELECT * FROM users");
}
?>

<?php
// ✅ Fixed: Proper validation
try {
    $pdo = new PDO("mysql:host=localhost;dbname=db", "user", "pass");
    $stmt = $pdo->prepare("SELECT * FROM users");
} catch (PDOException $e) {
    echo "Connection failed: " . $e->getMessage();
}
?>

9. Using mysql_* Functions

<?php
// ❌ Error: mysql_* returns resource/bool, not PDO
$connection = mysql_connect("localhost", "user", "pass");
mysql_select_db("database");
$stmt = $connection->prepare("SELECT * FROM users");  // Error!
?>

<?php
// ✅ Fixed: Use PDO
$pdo = new PDO("mysql:host=localhost;dbname=db", "user", "pass");
$stmt = $pdo->prepare("SELECT * FROM users");
?>

10. Variable Assignment Issue

<?php
// ❌ Error: Assignment returns false
$pdo = ($some_condition) ? false : new PDO("dsn", "user", "pass");
$stmt = $pdo->prepare("SELECT * FROM users");  // Error!
?>

<?php
// ✅ Fixed: Ensure PDO object
$pdo = ($some_condition) ? new PDO("good_dsn", "user", "pass") : new PDO("alternative_dsn", "user", "pass");
$stmt = $pdo->prepare("SELECT * FROM users");
?>

---

Quick Debugging Steps

1. Check PDO connection returns PDO object, not boolean
2. Verify connection string is correct
3. Use try/catch for PDO exceptions
4. Check error mode settings
5. Verify credentials are correct
6. Test connection separately before using prepare()

---

Prevention Tips

• Always check if PDO connection succeeded before using it
• Use try/catch blocks for PDO operations
• Set PDO error mode to exception: PDO::ERRMODE_EXCEPTION
• Verify connection string and credentials
• Don’t use error suppression (@) with PDO
• Use proper exception handling
• Test database connectivity separately
• Check PDO instance before calling methods

Remember: Ensure PDO connection is successful before calling prepare() or other PDO methods.