`isset()` vs. `empty()` in PHP: When Should I Use Each Function?

isset() vs. empty()

In programming, it's crucial to effectively check whether variables are set and have valid values. Two commonly used functions in PHP for these checks are isset() and empty(). This article explores the difference between the two and provides guidance on when to use each.

Using empty()

The empty() function makes a comprehensive assessment of whether a variable is empty. It not only checks if the variable exists (like isset()), but it also determines if it's an empty string, zero, a null value, or an empty array.

The following values are considered empty by empty():

• "" (empty string)
• 0 (integer zero)
• 0.0 (floating-point zero)
• "0" (string zero)
• NULL
• FALSE
• array() (empty array)
• unset variables in a class

Using isset()

Unlike empty(), isset() simply checks if a variable is set, regardless of its value. If the variable has been assigned any value, even null, isset() returns true. This is because isset() considers null as a valid value.

When to Use isset() and empty()

The choice between isset() and empty() depends on the specific need. If you need to verify that a variable is explicitly set and non-empty (including zero), use empty(). Conversely, if you want to check the mere presence of a variable, irrespective of its value, use isset().

An Example

Consider the following code:

• In this code, the isset() checks if $var exists, while the empty() checks if it's empty. The result would be 'not empty' because $var contains a non-empty string value.

On the other hand, if $var were set to null, isset() would return true (as it exists), but empty() would return true (as it's empty).

Conclusion:

The empty() function is more comprehensive than isset() as it both verifies if a variable is set and evaluates its emptiness. However, if you solely need to check if a variable exists, irrespective of its value, isset() is the appropriate choice.

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