How to pass code from header.php to footer.php

Question

I'm initializing a variable with a value in the header.php file. I want access to that value in footer.php, but it doesn't exist upon checking. Example:

header.php

$status = true;

footer.php

var_dump( $status ); // is null

What's a best practice for doing something in footer.php, or other files if they have the same behavior.

Answer 1

Avoid global variables, they could be overwritten by other code. You could use a helper function with a static internal variable instead. Sample code:

function wpse_69365_var_storage( $var = NULL )
{
    static $internal;

    if ( NULL !== $var )
    {
        $internal = $var;
    }

    return $internal;
}

// first call:
wpse_69365_var_storage( 4 );

// later call:
echo wpse_69365_var_storage(); // print 4

Answer 2

Based upon @toscho snippet, here's a real life example. Assuming that you don't need to access a var directly from inside the template file.

function wpse_69365_var_storage()
{
    static $internal;

    if ( 'wp_head' === current_filter() )
    {
        if ( /* Condition is met */ )
            return $internal = 4; // Set to what you need.

        return 'default_value';
    }

    return print $internal;
}
// Call in header.php:
add_action( 'wp_head', 'wpse_69365_var_storage' );
// Call in footer.php:
add_action( 'wp_footer', 'wpse_69365_var_storage' );