Fixing Strict Standards Errors: How to Properly Pass Variables by Reference in PHP

In this guide, we will discuss how to fix Strict Standards errors in PHP by properly passing variables by reference. This issue often arises when you are working with legacy code or upgrading your PHP version.

By following the steps outlined below, you will learn how to identify, address, and resolve these errors, ensuring that your PHP code is compliant and free of warnings.

Table of Contents

  1. Understanding Strict Standards Errors
  2. Properly Passing Variables by Reference
  3. FAQs

Understanding Strict Standards Errors

Strict Standards errors are generated when your code does not adhere to the best practices and guidelines recommended by the PHP development team. These errors, while not critical, can cause issues as you upgrade to later versions of PHP.

One common example of a Strict Standards error is when you pass a variable by reference when it should be passed by value. This can lead to unexpected behavior and poor performance.

Here is an example of a Strict Standards error message:

Strict Standards: Only variables should be passed by reference

This error occurs when you use a function or method that expects a reference to a variable, but you pass a value instead.

Learn more about Strict Standards errors

Properly Passing Variables by Reference

To fix the Strict Standards error mentioned above, you need to ensure that you pass variables by reference when required.

Follow these steps to properly pass variables by reference in PHP:

Step 1: Identify the Function or Method

First, find the function or method that generates the Strict Standards error. The error message should include the line number and file where the issue occurred.

Step 2: Modify the Function or Method Signature

Next, update the function or method signature to indicate that the variable should be passed by reference. To do this, add an ampersand (&) before the parameter in the signature.

For example, if the original function signature is:

function exampleFunction($variable) { ... }

Update it to:

function exampleFunction(&$variable) { ... }

Step 3: Update Function or Method Calls

Finally, ensure that you pass a variable, not a value, when calling the function or method.

For example, instead of:



$variable = someFunction();

By following these steps, you should be able to fix the Strict Standards error related to passing variables by reference in PHP.


Q: What is the difference between passing by reference and passing by value?

A: When you pass a variable by value, a copy of the variable is passed to the function or method. Any changes made to the variable within the function or method do not affect the original variable. When passing by reference, a reference to the original variable is passed, allowing the function or method to modify the original variable directly.

Q: Can I disable Strict Standards errors?

A: Yes, you can disable Strict Standards errors by adjusting your error_reporting settings in your php.ini file or at runtime using the error_reporting() function. However, it is recommended to fix the errors rather than suppressing them, as they may indicate potential issues in your code.

Q: How can I check if a variable is being passed by reference?

A: In PHP, you can use the debug_zval_dump() function to check if a variable is being passed by reference. This function displays information about a variable, including its reference count. If the reference count is greater than 1, the variable is being passed by reference.

Q: Can I pass arrays and objects by reference?

A: Yes, you can pass arrays and objects by reference in PHP. However, since PHP 5, objects are passed by reference by default, so you do not need to use the ampersand (&) when passing an object. For arrays, you can use the same syntax as for variables: include an ampersand (&) before the parameter in the function or method signature.

Q: What are the performance implications of passing variables by reference?

A: Passing variables by reference can improve performance in some cases, as it avoids creating a copy of the variable. However, it also increases the risk of unintended side effects, as changes made to the variable within the function or method affect the original variable. It is essential to use caution and follow best practices when passing variables by reference.

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