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What does the & symbol before variable names in a PHP function declaration signify?

The & symbol before variable names in a PHP function declaration signifies that the variable is being passed by reference rather than by value. This means that any changes made to the variable within the function will also affect the variable outside of the function. To implement this in PHP, simply add the & symbol before the variable name in the function declaration. This allows the function to directly modify the variable passed to it.

php 
function increment(&$num) {
    $num++;
}

$value = 5;
increment($value);
echo $value; // Output: 6

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