How to Determine if a Variable is Undefined or Empty in PHP?

How to Check for Undefined Variables in PHP

In JavaScript, developers can use the document.createTouch !== undefined statement to determine if a variable is defined. This differs from the isset() function in PHP, which only checks if a variable has been set to a value.

Checking for Undefined Variables in PHP

To check for an undefined variable in PHP, you can use the following statement:

<code class="php">$isTouch = isset($variable);</code>

This will return true if the $variable is defined and false if it is not.

Note: The isset() function returns TRUE if the variable exists and has a value other than NULL, and FALSE otherwise.

Checking for Empty Values

If you want to check for false, 0, etc., you can use the empty() function:

<code class="php">$isTouch = empty($variable);</code>

This will return TRUE for the following values:

• "" (an empty string)
• 0 (0 as an integer)
• 0.0 (0 as a float)
• "0" (0 as a string)
• NULL
• FALSE
• array() (an empty array)
• $var; (a variable declared, but without a value)

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