Why Does mysqli_stmt::bind_param() Throw a \'Type Definition String Mismatch\' Error?

mysqli_stmt::bind_param(): Type Definition String Mismatch

When executing prepared statements using mysqli_stmt::bind_param(), it's crucial that the number of elements in the type definition string matches the number of bind variables. This mismatch often leads to the error message, "Number of elements in type definition string doesn't match number of bind variables."

Problem Statement

The original query involves 65 variables being injected into a database using prepared statements. However, there is a discrepancy between the number of variables and the number of "s" characters in the type definition string.

Resolution

The number of characters in the type definition string ("s,s...") must be equal to the number of bind variables in the query. In this case, there are 65 bind variables, so the type definition string should contain 65 "s" characters.

Example

// Prepare query
$query3 = '... (65 bind variables here) ...';

// Prepare statement
$stmt = $dbConnection->prepare($query3);

// Bind parameters
$stmt->bind_param(
    "ssssssssssssssssssssssssssssssssssssssssssssssssssssssssss",
    // 65 variables listed here
);

// Execute query
$stmt->execute();

In this example, the type definition string contains 65 "s" characters, matching the number of variables in the query.

Common Pitfalls

• Using commas to separate characters in the type definition string
• Miscounting the number of placeholders in the query or variables used in the bind

Additional Considerations

• The type definition string should only contain characters that correspond to the data types of the variables being bound.
• The type definitions for double, float, and integer can be different for different database servers. Refer to the appropriate documentation for specific requirements.

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