The Distinction Between bindParam and bindValue: A Deeper Dive
In the realm of database programming with PHP's PDO framework, developers often encounter two methods: PDOStatement::bindParam() and PDOStatement::bindValue(). Although both serve the purpose of parameter binding, they exhibit subtle yet crucial differences that can impact code behavior.
bindParam: A Reference-Based Approach
The manual documentation for bindParam() highlights a significant distinction: it binds a variable as a reference, delaying its evaluation until PDOStatement::execute() is called. This means that any changes to the bound variable after binding will be reflected in the query execution.
For instance:
$sex = 'male'; $s = $dbh->prepare('SELECT name FROM students WHERE sex = :sex'); $s->bindParam(':sex', $sex); // Bind the variable using bindParam $sex = 'female'; $s->execute(); // Execution results in "WHERE sex = 'female'"
bindValue: Value-Based Binding
In contrast, PDOStatement::bindValue() binds the actual value of a variable at the time of binding. Subsequent modifications to the variable will not affect the query execution.
Consider the following case:
$sex = 'male'; $s = $dbh->prepare('SELECT name FROM students WHERE sex = :sex'); $s->bindValue(':sex', $sex); // Bind the value using bindValue $sex = 'female'; $s->execute(); // Execution results in "WHERE sex = 'male'"
This behavior can be crucial in situations where you intentionally want to bind a specific value and avoid the impact of later variable changes.
The above is the detailed content of bindParam vs. bindValue in PDO: When Should I Use Which?. For more information, please follow other related articles on the PHP Chinese website!

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