Difference between bindParam and bindValue in PHP

In PHP, bindParam and bindValue are methods used with PDO (PHP Data Objects) to bind parameters to SQL statements. While they both serve to pass values to SQL queries, they differ in how they handle these values:

1. bindParam:

   • Binding by Reference: bindParam binds a variable to a parameter in the SQL statement, and the variable is passed by reference. This means that if the value of the variable changes after the bindParam call, the new value will be used in the SQL execution.
   • Syntax:

     $stmt->bindParam(':param', $variable, PDO::PARAM_TYPE);
     

   • Example:

     $stmt = $pdo->prepare("INSERT INTO users (name, age) VALUES (:name, :age)");
     $name = 'John';
     $age = 25;
     $stmt->bindParam(':name', $name);
     $stmt->bindParam(':age', $age);
     $name = 'Doe'; // Changing the variable
     $stmt->execute(); // Will insert 'Doe' as name and 25 as age
     

2. bindValue:

   • Binding by Value: bindValue binds a value directly to a parameter in the SQL statement. Unlike bindParam, the value is not bound by reference, so the actual value at the time of bindValue call is used.
   • Syntax:

     $stmt->bindValue(':param', $value, PDO::PARAM_TYPE);
     

   • Example:

     $stmt = $pdo->prepare("INSERT INTO users (name, age) VALUES (:name, :age)");
     $stmt->bindValue(':name', 'John');
     $stmt->bindValue(':age', 25);
     $stmt->execute(); // Will always insert 'John' as name and 25 as age
     

Key Differences:

• Reference vs. Value: bindParam uses a reference to a variable, which means the bound variable can change before the statement is executed. bindValue uses the actual value provided at the time of the method call.
• Use Case: Use bindParam when you need to bind a variable that might change before execution. Use bindValue when you have a constant or fixed value to bind.

Both methods are useful depending on the context of how you are handling your data and the specific requirements of your SQL execution logic.