bindParam vs. bindValue in PDO: When Should You Use Which?

Understanding the Distinction between bindParam and bindValue in PDO

PDO provides two crucial methods for parameter binding: bindParam and bindValue. Grasping their distinctions is paramount for effective data manipulation in PHP applications.

bindParam vs. bindValue

The primary difference lies in the nature of parameter binding. bindParam binds a variable by reference, while bindValue binds its value directly. This distinction becomes evident when the variable is modified after binding.

Impact of Variable Modification

When using bindParam, any changes made to the bound variable before executing the statement will affect the query's execution. This is because the variable is bound as a reference.

Example:

$sex = 'male';
$s = $dbh->prepare('SELECT name FROM students WHERE sex = :sex');
$s->bindParam(':sex', $sex);
$sex = 'female';
$s->execute(); // executed with WHERE sex = 'female'

Conversely, bindValue binds the variable's value at the time of execution. Subsequent modifications to the variable have no impact on the query.

Example:

$sex = 'male';
$s = $dbh->prepare('SELECT name FROM students WHERE sex = :sex');
$s->bindValue(':sex', $sex);
$sex = 'female';
$s->execute(); // executed with WHERE sex = 'male'

Choice of Binding Method

The selection of bindParam or bindValue depends on the use case. If the variable's value needs to change before query execution, bindParam is preferred. Otherwise, bindValue may suffice.

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