Binding Parameters for WHERE IN Clause with PDO
When using PDO to execute a query with a WHERE IN clause, parameter binding may not work as expected. As demonstrated in the provided code snippet, binding a comma-separated list of values to the :ids parameter results in a count of 1, despite there being multiple values in the array.
Explanation
The issue lies in how the IN clause expects values to be formatted. When binding an array, PHP combines all the elements into a single string, which is treated as one parameter by the database. This results in the following query being executed:
SELECT foo FROM bar WHERE ids IN ('1,2,3')
However, the IN clause requires each value to be an individual parameter:
SELECT foo FROM bar WHERE ids IN (1, 2, 3)
Solution
To resolve this, one must manually insert the IN list into the query string:
'SELECT foo FROM bar WHERE ids IN (' . $myArray .')'
Alternatively, one can use the bindParam method to bind individual values rather than an array.
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