PHP 7.4 compatibility fix / implode argument order
PHP 7.4 compatibility fix / implode argument order

`implode()` takes two parameters, `$glue` and `$pieces`.
For historical reasons, `implode()` accepted these parameters in either order, though it was recommended to use the documented argument order of `implode( $glue, $pieces )`.

PHP 7.4 deprecates the tolerance for passing the parameters for `implode()` in reverse order.
PHP 8.0 is expected to remove the tolerance for this completely.

Refs:
* https://wiki.php.net/rfc/deprecations_php_7_4#implode_parameter_order_mix
* https://php.net/manual/en/function.implode.php

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