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Question: 1 / 400

What will happen if you try to access an undefined constant in PHP?

It will throw a syntax error

It will return null

It will generate a warning

When you attempt to access an undefined constant in PHP, the language will generate a warning. PHP tries to interpret the undefined constant as a string by taking its name and converting it to a string. If the constant name does not exist, PHP issues a warning to inform you of this issue, but the script will continue to execute.

For example, if you try to access `MY_CONSTANT` and it has not been defined using the `define()` function or as a constant in a class, PHP interprets it as a string `'MY_CONSTANT'`. Consequently, the warning provides a soft alert of the problem while allowing the rest of the code to run.

Understanding this behavior is essential for debugging and maintaining robust code in PHP applications. It highlights the importance of constant definitions and the attention needed for potential typos or overlooked definitions in your code.

Ace the Zend Certified PHP Engineer Challenge 2025 – Power Up Your PHP Skills!

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