In php, isset() functions and examples

In php, the function and examples of isset()
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Check if the variable is defined

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Determine whether the variable has been configured.
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isset
Determines whether the variable has been set.
Syntax: int isset(mixed var);
Return value: integer
Function type: PHP system function
Content description
This function is used to test variables Has it been set? If the variable already exists, a true value is returned. Otherwise a false value is returned.

Usage examples
<?php
$a = “test”;
echo isset($a); // true
unset($a );
echo isset($a); // false
?>